diff src/nucleus/gcc/tct.S @ 0:4e78acac3d88

src/{condat,cs,gpf,nucleus}: import from Selenite
author Mychaela Falconia <falcon@freecalypso.org>
date Fri, 16 Oct 2020 06:23:26 +0000
parents
children
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--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/nucleus/gcc/tct.S	Fri Oct 16 06:23:26 2020 +0000
@@ -0,0 +1,3003 @@
+/*
+ ************************************************************************
+ *                                                                       
+ *               Copyright Mentor Graphics Corporation 2002              
+ *                         All Rights Reserved.                          
+ *                                                                       
+ * THIS WORK CONTAINS TRADE SECRET AND PROPRIETARY INFORMATION WHICH IS  
+ * THE PROPERTY OF MENTOR GRAPHICS CORPORATION OR ITS LICENSORS AND IS   
+ * SUBJECT TO LICENSE TERMS.                                             
+ *                                                                       
+ ************************************************************************
+ ************************************************************************
+ *                                                                       
+ * FILE NAME                              VERSION                        
+ *                                                                       
+ *      tct.s                   Nucleus PLUS\ARM925\Code Composer 1.14.1 
+ *                                                                       
+ * COMPONENT                                                             
+ *                                                                       
+ *      TC - Thread Control                                              
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This file contains the target processor dependent routines for   
+ *      performing target-dependent scheduling functions.                
+ *                                                                       
+ * FUNCTIONS                                                             
+ *                                                                       
+ *      TCT_Control_Interrupts              Enable / disable interrupts  
+ *                                          by changing                  
+ *                                          TCD_Interrupt_Level          
+ *      TCT_Local_Control_Interrupts        Enable/disable interrupts    
+ *                                          by not changing              
+ *                                          TCD_Interrupt_Level          
+ *      TCT_Restore_Interrupts              Restores interrupts to the   
+ *                                          level in TCD_Interrupt_Level 
+ *      TCT_Build_Task_Stack                Build initial task stack     
+ *      TCT_Build_HISR_Stack                Build initial HISR stack     
+ *      TCT_Build_Signal_Frame              Build signal handler frame   
+ *      TCT_Check_Stack                     Check current stack          
+ *      TCT_Schedule                        Schedule the next thread     
+ *      TCT_Control_To_Thread               Transfer control to a thread 
+ *      TCT_Control_To_System               Transfer control from thread 
+ *      TCT_Signal_Exit                     Exit from signal handler     
+ *      TCT_Current_Thread                  Returns a pointer to current 
+ *                                            thread                     
+ *      TCT_Set_Execute_Task                Sets TCD_Execute_Task under  
+ *                                            protection from interrupts 
+ *      TCT_Protect                         Protect critical section     
+ *      TCT_Unprotect                       Unprotect critical section   
+ *      TCT_Unprotect_Specific              Release specific protection  
+ *      TCT_Set_Current_Protect             Set the thread's current     
+ *                                            protection field           
+ *      TCT_Protect_Switch                  Switch to protected thread   
+ *      TCT_Schedule_Protected              Schedule the protected thread
+ *      TCT_Interrupt_Context_Save          Save interrupted context     
+ *      TCT_Interrupt_Context_Restore       Restore interrupted context  
+ *      TCT_Activate_HISR                   Activate a HISR              
+ *      TCT_HISR_Shell                      HISR execution shell         
+ *                                                                       
+ * DEPENDENCIES                                                          
+ *                                                                       
+ *      cs_extr.h                           Common Service functions     
+ *      tc_extr.h                           Thread Control functions     
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      B. Ronquillo     08-28-2002           Released version 1.14.1    
+ *                                                                       
+ ************************************************************************
+ */
+
+#define         NU_SOURCE_FILE
+
+/*
+ ******************************
+ * INCLUDE ASSEMBLY CONSTANTS *
+ ******************************
+ * Define constants used in low-level initialization. 
+ */
+
+#include "asm_defs.h"
+
+	.code 32
+
+/* TCT_System_Limit is a global variable defined in this module */
+
+	.comm	TCT_System_Limit,4,4
+
+    .text
+
+/*
+ **********************************
+ * LOCAL VARIABLE DECLARATIONS    *
+ **********************************
+ * Define pointers to system variables so their addresses may be obtained in a
+ * pc-relative manner. 
+ */
+
+System_Limit:
+        .word   TCT_System_Limit
+
+Int_Level:
+        .word   TCD_Interrupt_Level
+
+Task_Shell:
+        .word   TCC_Task_Shell
+
+HISR_Shell:
+        .word   TCT_HISR_Shell
+
+Signal_Shell:
+        .word   TCC_Signal_Shell
+
+Current_Thread:
+        .word   TCD_Current_Thread
+
+Execute_HISR:
+        .word   TCD_Execute_HISR
+
+Execute_Task:
+        .word   TCD_Execute_Task
+
+Time_Slice:
+        .word   TMD_Time_Slice
+
+Slice_State:
+        .word   TMD_Time_Slice_State
+
+System_Stack:
+        .word   TCD_System_Stack
+
+Int_Count:
+        .word   TCD_Interrupt_Count
+
+HISR_Tails:
+        .word   TCD_Active_HISR_Tails
+
+HISR_Heads:
+        .word   TCD_Active_HISR_Heads
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ * TCT_Control_Interrupts                                                
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function enables and disables interrupts as specified by    
+ *      the caller.  Interrupts disabled by this call are left disabled  
+ *      until the another call is made to enable them.                   
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      Application                                                      
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      new_level                           New interrupt enable level   
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      old_level                           Previous interrupt enable    
+ *                                            level                      
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *      C. Meredith     03-01-1994      Lockout interrupts while setting 
+ *                                        up the new level, resutling in 
+ *                                        version 1.1                    
+ *      D. Lamie        03-18-1994      Verified version 1.1             
+ *      M. Trippi       02-03-1997      Masked the return value to only  
+ *                                        return the interrupt bits.     
+ *                                        (SPR0252)                      
+ *                                                                       
+ ************************************************************************
+ */
+
+@INT TCT_Control_Interrupts (INT new_level)
+@{
+
+        .globl  TCT_Control_Interrupts
+TCT_Control_Interrupts:
+
+@INT     old_level;                          Old interrupt level      
+
+@    lock out all interrupts before any checking or changing
+
+@    Obtain the current interrupt lockout posture. 
+@    old_level =  TCD_Interrupt_Level;
+
+@    Setup new interrupt lockout posture. 
+@    TCD_Interrupt_Level =  new_level;
+
+@    renable interrupts for the specified lockout
+
+@    Return old interrupt lockout level. 
+@    return(old_level);
+
+        MRS     r2,CPSR                     @ Pickup current CPSR
+        ORR     r2,r2,#LOCKOUT              @ Build lockout CPSR
+        MSR     CPSR,r2                     @ Lockout interrupts temporarily
+        LDR     r1, Int_Level               @ Pickup interrupt level
+        LDR     r3,[r1, #0]                 @ Pickup current interrupt lockout
+        BIC     r2,r2,#LOCK_MSK             @ Clear lockout mask
+        ORR     r2,r2,r0                    @ Build new CPSR with appropriate
+                                            @   interrupts locked out
+        STR     r0,[r1,#0]                  @ Save current lockout 
+        MSR     CPSR,r2                     @ Setup new CPSR lockout bits
+        AND     r0,r3,#LOCK_MSK             @ Return previous lockout (SPR0252)
+      
+        BX      r14                         @ Return to caller
+
+@}    
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ * TCT_Local_Control_Interrupts                                          
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function enables and disables interrupts as specified by    
+ *      the caller.                                                      
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      Application                                                      
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      new_level                           New interrupt enable level   
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      old_level                           Previous interrupt enable    
+ *                                            level                      
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      C. Meredith     03-01-1994      Created initial version 1.1      
+ *      D. Lamie        03-18-1994      Verified version 1.1             
+ *      M. Trippi       02-03-1997      Masked the return value to only  
+ *                                        return the interrupt bits.     
+ *                                        (SPR0252)                      
+ *                                                                       
+ ************************************************************************
+ */
+
+@INT TCT_Local_Control_Interrupts (INT new_level)
+@{
+
+	.globl  TCT_Local_Control_Interrupts
+TCT_Local_Control_Interrupts:
+
+@INT     old_level;                          Old interrupt level      
+
+@    read in the old level
+@    old_level = current interrupt level of processor;
+
+        MRS     r2,CPSR                     @ Pickup current CPSR
+        MOV     r3,r2                       @ save the old level
+
+@    clear out the old level and set the new level
+@    current interrupt level of processor &= ~LOCKOUT;
+@    current interrupt level of processor |= new_level;
+
+        BIC     r2,r2,#LOCK_MSK             @ Clear all current interrupts
+        ORR     r2,r2,r0                    @ Build new CPSR with new
+                                            @ interrupt level
+        MSR     CPSR,r2                     @ Setup new CPSR interrupt bits
+
+@    Return old interrupt lockout level. 
+@    return(old_level);
+
+        AND     r0,r3,#LOCK_MSK             @ Return previous lockout (SPR0252)
+       
+        BX      r14                         @ Return to caller
+
+@}    
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *  TCT_Restore_Interrupts                                               
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function restores interrupts to that specified in the global
+ *      TCD_Interrupt_Level variable.                                    
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      Application                                                      
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      None.                                                            
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      None.                                                            
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      C. Meredith     03-01-1994      Created initial version 1.1      
+ *      D. Lamie        03-18-1994      Verified version 1.1             
+ *                                                                       
+ ************************************************************************
+ */
+
+@VOID TCT_Restore_Interrupts  (VOID)
+@{
+
+	.globl  TCT_Restore_Interrupts
+TCT_Restore_Interrupts:
+
+@ Lock out all interrupts before any checking or changing
+@ Obtain the current interrupt lockout posture. 
+@ Reload the level base on the TCD_Interrupt_Level variable
+
+        MRS     r1,CPSR                     @ Pickup current CPSR
+        MOV     r2,r1                       @ save the CPSR value
+        ORR     r1,r1,#LOCKOUT              @ Build lockout CPSR
+        MSR     CPSR,r1                     @ Lockout interrupts temporarily
+        BIC     r2,r2,#LOCK_MSK             @ Clear current interrupt levels
+        LDR     r1,Int_Level                @ Load address of TCD_Interrupt_Level
+        LDR     r0,[r1, #0]                 @ Pickup current interrupt lockout
+        ORR     r2,r2,r0                    @ Build new CPSR with appropriate
+                                            @ interrupts locked out
+        MSR     CPSR,r2                     @ Setup new CPSR lockout bits
+
+        BX      r14                         @ Return to caller
+
+@}    
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *      TCT_Build_Task_Stack                                             
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function builds an initial stack frame for a task.  The     
+ *      initial stack contains information concerning initial values of  
+ *      registers and the task's point of entry.  Furthermore, the       
+ *      initial stack frame is in the same form as an interrupt stack    
+ *      frame.                                                           
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      TCC_Create_Task                     Create a new task            
+ *      TCC_Reset_Task                      Reset the specified task     
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      task                                Task control block pointer   
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *                                                                       
+ ************************************************************************
+ */
+
+@VOID  TCT_Build_Task_Stack(TC_TCB *task)
+@{
+
+	.globl  TCT_Build_Task_Stack
+TCT_Build_Task_Stack:
+
+    @ Pickup the stack base. 
+@    REG_Stack_Base =  (BYTE_PTR) task -> tc_stack_start;
+
+        LDR     r2,[r0,#0x24]               @ Pickup the stack starting address
+
+    @ Pickup the stack size. 
+@    REG_Stack_Size =  task -> tc_stack_size;
+
+        LDR     r1,[r0,#0x30]               @ Pickup the stack size in bytes
+
+    @ Calculate the stack ending address. 
+@    REG_Stack_End =  REG_Stack_Base + REG_Stack_Size - 1;
+
+        ADD     r3,r1,r2                    @ Compute the beginning of stack
+        BIC     r3,r3,#3                    @ Insure word alignment
+        SUB     r3,r3,#4                    @ Reserve a word
+
+    @ Save the stack ending address. 
+@    task -> tc_stack_end =  REG_Stack_End;
+
+        STR     r3,[r0,#0x28]               @ Save the stack ending address
+
+    @ Reference the task shell. 
+@    REG_Function_Ptr =  (VOID *) TCC_Task_Shell;
+
+@ Build an initial stack.  This initial stack frame facilitates an 
+@ interrupt return to the TCC_Task_Shell function, which in turn 
+@ invokes the application task.  The initial stack frame has the 
+@ following format:
+
+@               (Lower Address) Stack Top ->    1       (Interrupt stack type)
+@                                               CPSR    Saved CPSR
+@                                               r0      Saved r0
+@                                               r1      Saved r1
+@                                               r2      Saved r2
+@                                               r3      Saved r3
+@                                               r4      Saved r4
+@                                               r5      Saved r5
+@                                               r6      Saved r6
+@                                               r7      Saved r7
+@                                               r8      Saved r8
+@                                               r9/sb   Saved r9/sl
+@                                               r10/sl   Saved r10/sl
+@                                               fp      Saved fp
+@                                               r12      Saved r12
+@                                               r13      Saved r13
+@                                               r14      Saved r14
+@               (Higher Address) Stack Bottom-> r15      Saved r15
+  
+
+        LDR     r2, Task_Shell              @ Pickup address of shell entry
+        STR     r2,[r3], #-4                @ Store entry address on stack
+        MOV     r2,#0                       @ Clear value for initial registers
+        STR     r2,[r3], #-4                @ Store initial r14
+        ADD     r2,r3,#8                    @ Compute initial r13
+        STR     r2,[r3], #-4                @ Store initial r13 (Stack Bottom)
+        STR     r2,[r3], #-4                @ Store initial r12
+        STR     r2,[r3], #-4                @ Store initial fp
+        LDR     r2,[r0,#0x24]               @ Pickup the stack starting address
+        STR     r2,[r3], #-4                @ Store initial r10/sl
+        MOV     r2,#0                       @ Clear value for initial registers
+        STR     r2,[r3], #-4                @ Store initial r9/sb
+        STR     r2,[r3], #-4                @ Store initial r8
+        STR     r2,[r3], #-4                @ Store initial r7
+        STR     r2,[r3], #-4                @ Store initial r6
+        STR     r2,[r3], #-4                @ Store initial r5
+        STR     r2,[r3], #-4                @ Store initial r4
+        STR     r2,[r3], #-4                @ Store initial r3
+        STR     r2,[r3], #-4                @ Store initial r2
+        STR     r2,[r3], #-4                @ Store initial r1
+        STR     r2,[r3], #-4                @ Store initial r0
+        MSR     CPSR_f,r2                   @ Clear the flags
+        MRS     r2,CPSR                     @ Pickup the CPSR
+        BIC     r2,r2,#LOCK_MSK             @ Clear initial interrupt lockout
+        STR     r2,[r3], #-4                @ Store CPSR on the initial stack
+        MOV     r2,#1                       @ Build interrupt stack type (1)
+        STR     r2,[r3, #0]                 @ Store stack type on the top 
+
+    @ Save the minimum amount of remaining stack memory. 
+@    task -> tc_stack_minimum =  REG_Stack_Size - 72;
+
+        MOV     r2,#72                      @ Size of interrupt stack frame
+        SUB     r1,r1,r2                    @ Compute minimum available bytes
+        STR     r1,[r0, #0x34]              @ Save in minimum stack area
+
+    @ Save the new stack pointer into the task's control block. 
+@    task -> tc_stack_pointer =  (VOID *) Stack_Top;
+
+        STR     r3,[r0, #0x2C]              @ Save stack pointer
+
+        BX      r14                         @ Return to caller
+
+@}
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *      TCT_Build_HISR_Stack                                             
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function builds an HISR stack frame that allows quick       
+ *      scheduling of the HISR.                                          
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      TCC_Create_HISR                     Create HISR function         
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      hisr                                HISR control block pointer   
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *                                                                       
+ ************************************************************************
+ */
+
+@VOID  TCT_Build_HISR_Stack(TC_HCB *hisr)
+@{
+
+	.globl  TCT_Build_HISR_Stack
+TCT_Build_HISR_Stack:
+
+    @ Pickup the stack base. 
+@    REG_Stack_Base =  (BYTE_PTR) hisr -> tc_stack_start;
+
+        LDR     r2,[r0,#0x24]               @ Pickup the stack starting address
+
+    @ Pickup the stack size. 
+@    REG_Stack_Size =  hisr -> tc_stack_size;
+
+        LDR     r1,[r0,#0x30]               @ Pickup the stack size in bytes
+
+    @ Calculate the stack ending address. 
+@    REG_Stack_End =  REG_Stack_Base + REG_Stack_Size;
+
+        ADD     r3,r1,r2                    @ Compute the beginning of stack
+        BIC     r3,r3,#3                    @ Insure word alignment
+        SUB     r3,r3,#4                    @ Reserve a word
+
+    @ Save the stack ending address. 
+@    hisr -> tc_stack_end =  REG_Stack_End;
+
+        STR     r3,[r0,#0x28]               @ Save the stack ending address
+
+    @ Reference the HISR shell. 
+@    REG_Function_Ptr =  (VOID *) TCT_HISR_Shell;
+
+@ Build an initial stack.  This initial stack frame facilitates an 
+@ solicited return to the TCT_HISR_Shell function, which in turn 
+@ invokes the appropriate HISR.  The initial HISR stack frame has the 
+@ following format:
+
+@               (Lower Address) Stack Top ->    0       (Solicited stack type)
+@                !!FOR THUMB ONLY!!             0/0x20  Saved state mask
+@                                               r4      Saved r4
+@                                               r5      Saved r5
+@                                               r6      Saved r6
+@                                               r7      Saved r7
+@                                               r8      Saved r8
+@                                               r9/sb   Saved r9/sl
+@                                               r10/sl   Saved r10/sl
+@                                               fp      Saved fp
+@                                               r12      Saved r12
+@               (Higher Address) Stack Bottom-> r15      Saved r15
+   
+
+        LDR     r2,HISR_Shell               @ Pickup address of shell entry
+        STR     r2,[r3], #-4                @ Store entry address on stack
+        ADD     r2,r3,#4                    @ Compute initial r13
+        STR     r2,[r3], #-4                @ Store initial r12
+        STR     r2,[r3], #-4                @ Store initial fp
+        LDR     r2,[r0,#0x24]               @ Pickup the stack starting address
+        STR     r2,[r3], #-4                @ Store initial r10/sl
+        MOV     r2,#0                       @ Clear value for initial registers
+        STR     r2,[r3], #-4                @ Store initial r9/sb
+        STR     r2,[r3], #-4                @ Store initial r8
+        STR     r2,[r3], #-4                @ Store initial r7
+        STR     r2,[r3], #-4                @ Store initial r6
+        STR     r2,[r3], #-4                @ Store initial r5
+        STR     r2,[r3], #-4                @ Store initial r4
+#if 1	/* was .if THUMB */
+        STR     r2,[r3], #-4                @ Store initial state mask
+#endif
+        STR     r2,[r3, #0]                 @ Store solicited stack type on the
+                                            @ top of the stack 
+
+    @ Save the minimum amount of remaining stack memory. 
+@    hisr -> tc_stack_minimum =  REG_Stack_Size - (ARM)44 or (THUMB)48;
+
+#if 1	/* was .if THUMB */
+        MOV     r2,#48                      @ Size of solicited stack frame
+#else
+        MOV     r2,#44                      @ Size of solicited stack frame
+#endif
+
+        SUB     r1,r1,r2                    @ Compute minimum available bytes
+        STR     r1,[r0, #0x34]              @ Save in minimum stack area
+
+    @ Save the new stack pointer into the task's control block. 
+@    hisr -> tc_stack_pointer =  (VOID *) Stack_Top;
+
+        STR     r3,[r0, #0x2C]              @ Save stack pointer
+
+        BX      r14                         @ Return to caller
+
+@}
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *      TCT_Build_Signal_Frame                                           
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function builds a frame on top of the task's stack to       
+ *      cause the task's signal handler to execute the next time         
+ *      the task is executed.                                            
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      TCC_Send_Signals                    Send signals to a task       
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      task                                Task control block pointer   
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *                                                                       
+ ************************************************************************
+ */
+
+@VOID  TCT_Build_Signal_Frame(TC_TCB *task)
+@{
+
+	.globl  TCT_Build_Signal_Frame
+TCT_Build_Signal_Frame:
+
+    @ Pickup the stack pointer. 
+@    REG_Stack_Ptr =  (BYTE_PTR) task -> tc_stack_pointer;
+
+        LDR     r3,[r0,#0x2c]               @ Pickup the current stack pointer
+
+    @ Reference the Signal shell. 
+@    REG_Function_Ptr =  (VOID *) TCC_Signal_Shell;
+
+@ Build a signal stack.  This signal stack frame facilitates an 
+@ solicited return to the TCC_Signal_Shell function, which in turn 
+@ invokes the appropriate signal handler.  The initial HISR stack frame 
+@ has the following format:
+
+@               (Lower Address) Stack Top ->    0       (Solicited stack type)
+@                !!FOR THUMB ONLY!!             0/0x20  Saved state mask
+@                                               r4      Saved r4
+@                                               r5      Saved r5
+@                                               r6      Saved r6
+@                                               r7      Saved r7
+@                                               r8      Saved r8
+@                                               r9/sb   Saved r9/sl
+@                                               r10/sl   Saved r10/sl
+@                                               fp      Saved fp
+@                                               r12      Saved r12
+@               (Higher Address) Stack Bottom-> r15      Saved r15
+   
+
+        LDR     r2,Signal_Shell             @ Pickup address of shell entry
+        SUB     r3,r3,#4
+        STR     r2,[r3], #-4                @ Store entry address on stack
+        ADD     r2,r3,#4                    @ Compute initial r13
+        STR     r2,[r3], #-4                @ Store initial r12
+        STR     r2,[r3], #-4                @ Store initial fp
+        LDR     r2,[r0,#0x24]               @ Pickup the stack starting address
+        STR     r2,[r3], #-4                @ Store initial r10/sl
+        MOV     r2,#0                       @ Clear value for initial registers
+        STR     r2,[r3], #-4                @ Store initial r9/sb
+        STR     r2,[r3], #-4                @ Store initial r8
+        STR     r2,[r3], #-4                @ Store initial r7
+        STR     r2,[r3], #-4                @ Store initial r6
+        STR     r2,[r3], #-4                @ Store initial r5
+        STR     r2,[r3], #-4                @ Store initial r4
+#if 0
+        MOV     r1,#0x20                    @ Get initial state mask
+        STR     r1,[r3], #-4                @ Store initial state mask  
+#else
+	STR	r2,[r3], #-4		    @ TCC_Signal_Shell is an ARM proc
+#endif
+
+        STR     r2,[r3, #0]                 @ Store solicited stack type on the
+                                            @ top of the stack 
+
+    @ Save the new stack pointer into the task's control block. 
+@    task -> tc_stack_pointer =  (VOID *) (REG_Stack_Ptr - REG_Stack_Size);
+
+        STR     r3,[r0, #0x2C]              @ Save stack pointer
+
+        BX      r14                         @ Return to caller
+
+@}
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *      TCT_Check_Stack                                                  
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function checks the current stack for overflow conditions.  
+ *      Additionally, this function keeps track of the minimum amount    
+ *      of stack space for the calling thread and returns the current    
+ *      available stack space.                                           
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      TCC_Send_Signals                    Send signals to a task       
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      ERC_System_Error                    System error handler         
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      available bytes in stack                                         
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *                                                                       
+ ************************************************************************
+ */
+
+@UNSIGNED  TCT_Check_Stack(void)
+@{
+
+	.globl  TCT_Check_Stack
+TCT_Check_Stack:
+
+@TC_TCB         *thread;
+@UNSIGNED       remaining;
+
+    @ Pickup the current task/HISR pointer. 
+@    thread =  (TC_TCB *) TCD_Current_Thread;
+
+        LDR     r0,Current_Thread           @ Pickup address of thread pointer
+        LDR     r0,[r0,#0]                  @ Pickup thread pointer
+
+    @ Determine if there is a current thread. 
+@    if (thread)
+@    {
+
+        CMP     r0,#0                       @ Determine if a thread is active
+        MOV     r3,#0                       @ Default remaining value
+        BEQ     TCT_Skip_Stack_Check        @ If NU_NULL, skip stack checking
+
+        @ Determine if the stack pointers are out of range. 
+@        if ((thread -> tc_stack_pointer < thread -> tc_stack_start) ||
+@            (thread -> tc_stack_pointer > thread -> tc_stack_end))
+
+        LDR     r2,[r0,#0x24]               @ Pickup start of stack area
+        CMP     r13,r2                      @ Compare with current stack ptr
+        BLT     TCT_Stack_Range_Error       @ If less, stack is out of range
+        LDR     r1,[r0,#0x28]               @ Pickup end of stack area
+        CMP     r13,r1                      @ Compare with current stack ptr
+        BLE     TCT_Stack_Range_Okay        @ If less, stack range is okay
+
+            @ Stack overflow condition exits. 
+@            ERC_System_Error(NU_STACK_OVERFLOW);
+
+TCT_Stack_Range_Error:
+
+        STR     r14,[r13, #4]!              @ Store r14 on the stack
+        MOV     r0,#3                       @ Build NU_STACK_OVERFLOW code
+        BL      ERC_System_Error            @ Call system error handler.  Note:
+                                            @ control is not returned!  
+                                            @ Examine stack to find return 
+                                            @ address of this routine.
+
+TCT_Stack_Range_Okay:
+
+    @ Calculate the amount of available space on the stack. 
+@    remaining =  (BYTE_PTR) thread -> tc_stack_pointer -
+@                        (BYTE_PTR) thread -> tc_stack_start;
+
+        SUB     r3,r13,r2                   @ Calculate remaining stack size
+
+    @ Determine if there is enough memory on the stack to save all of the
+    @ registers. 
+@    if (remaining < 80)
+
+        CMP     r3,#80                      @ Is there enough room for an 
+                                            @ interrupt frame?
+        BCS     TCT_No_Stack_Error          @ If so, no stack overflow yet
+
+            @ Stack overflow condition is about to happen. 
+@            ERC_System_Error(NU_STACK_OVERFLOW);
+
+        STR     r14,[r13, #4]!              @ Store r14 on the stack
+        MOV     r0,#3                       @ Build NU_STACK_OVERFLOW code
+        BL      ERC_System_Error            @ Call system error handler.  Note:
+                                            @ control is not returned!  
+                                            @ Examine stack to find return 
+                                            @ address of this routine.
+
+TCT_No_Stack_Error:
+
+    @ Determine if this is a new minimum amount of stack space. 
+@    if (remaining < thread -> tc_stack_minimum)
+
+        LDR     r2,[r0,#0x34]
+        CMP     r3,r2
+        STRCC   r3,[r0,#0x34]
+
+        @ Save the new stack minimum. 
+@       thread -> tc_stack_minimum =  remaining;
+@    }
+@    else
+
+        @ Set the remaining bytes to 0. 
+@        remaining =  0;
+
+    @ Return the remaining number of bytes on the stack. 
+@    return(remaining);
+
+TCT_Skip_Stack_Check:
+        MOV     r0,r3                       @ Return remaining bytes
+
+        BX      r14                         @ Return to caller
+
+@}
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *      TCT_Schedule                                                     
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function waits for a thread to become ready.  Once a thread 
+ *      is ready, this function initiates a transfer of control to that  
+ *      thread.                                                          
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      INC_Initialize                      Main initialization routine  
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      TCT_Control_To_Thread               Transfer control to a thread 
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      TCD_Execute_Task                    Pointer to task to execute   
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *                                                                       
+ ************************************************************************
+ */
+
+@VOID  TCT_Schedule(void)
+@{
+
+	.globl  TCT_Schedule
+TCT_Schedule:
+
+    @ Restore interrupts according to the value contained in 
+@    TCD_Interrupt_Level.
+
+        LDR     r1,Int_Level                @ Build address of interrupt level
+        MRS     r0,CPSR                     @ Pickup current CPSR
+        LDR     r2,[r1, #0]                 @ Pickup current interrupt lockout
+        BIC     r0,r0,#LOCK_MSK             @ Clear the interrupt lockout bits
+        ORR     r0,r0,r2                    @ Build new interrupt lockout CPSR
+        MSR     CPSR,r0                     @ Setup new CPSR 
+        LDR     r2,Execute_HISR             @ Pickup TCD_Execute_HISR address
+        LDR     r3,Execute_Task             @ Pickup TCD_Execute_Task address
+
+#ifdef INCLUDE_PROVIEW
+@ Nucleus ProView Hook
+@ We check if upon entering TCT_Schedule we already have a task to excute.
+@ if not, we start IDLE.
+        LDR     r0,[r2, #0]                 @ Pickup highest priority HISR ptr
+        CMP     r0,#0                       @ Is there a HISR active?
+        BNE     TCT_Schedule_Thread         @ Found an HISR
+        LDR     r0,[r3, #0]                 @ Pickup highest priority Task ptr
+        CMP     r0,#0                       @ Is there a task active?
+        BNE     TCT_Schedule_Thread         @ If not, start IDLE.
+        STR     r2,[r13, #-4]!              @ Save r2 on the stack
+        STR     r3,[r13, #-4]!              @ Save r3 on the stack
+        BL      _NU_Idle_Hook
+        LDR     r3,[r13], #4                @ Recover r2
+        LDR     r2,[r13], #4                @ Recover r3
+#endif
+
+
+    @ Wait until a thread (task or HISR) is available to execute.
+@    do
+@    {
+	.globl  TCT_Schedule_Loop
+TCT_Schedule_Loop:
+
+@    } while ((!TCD_Execute_HISR) && (!TCD_Execute_Task));
+
+        LDR     r0,[r2, #0]                 @ Pickup highest priority HISR ptr
+        CMP     r0,#0                       @ Is there a HISR active?
+        BNE     TCT_Schedule_Thread         @ Found an HISR
+        LDR     r0,[r3, #0]                 @ Pickup highest priority Task ptr
+        CMP     r0,#0                       @ Is there a task active?
+#if 1 /* was CONFIG_INCLUDE_L1 in Citrine */
+	BEQ	_GSM_Small_Sleep
+#else
+	BEQ	TCT_Schedule_Loop           @ If not, continue the search
+#endif
+
+    @ Yes, either a task or an HISR is ready to execute.  Lockout 
+    @ interrupts while the thread is transferred to.
+
+TCT_Schedule_Thread:
+        MRS     r1,CPSR                     @ Pickup CPSR again
+        ORR     r1,r1,#LOCKOUT              @ Build interrupt lockout value
+        MSR     CPSR,r1                     @ Lockout interrupts
+
+@ Transfer control to the thread by falling through to the following
+@ routine.
+@}
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *      TCT_Control_To_Thread                                            
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function transfers control to the specified thread.  Each   
+ *      time control is transferred to a thread, its scheduled counter   
+ *      is incremented.  Additionally, time-slicing for task threads is  
+ *      enabled in this routine.  The TCD_Current_Thread pointer is      
+ *      setup by this function.                                          
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      TCT_Schedule                        Indirectly called            
+ *      TCT_Protect                         Protection task switch       
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      thread                              Thread control block pointer 
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *                                                                       
+ ************************************************************************
+ */
+
+@VOID  TCT_Control_To_Thread(TC_TCB *thread)
+@{
+TCT_Control_To_Thread:
+
+    @ Setup the current thread pointer.
+@    TCD_Current_Thread =  (VOID *) thread;
+
+        LDR     r1,Current_Thread           @ Pickup current thread ptr address
+        LDR     r2,[r0, #0x1c]              @ Pickup scheduled count
+        STR     r0,[r1, #0]                 @ Setup current thread pointer
+
+    @ Increment the thread scheduled counter.
+@    thread -> tc_scheduled++;
+
+        LDR     r3,[r0, #0x20]              @ Pickup time slice value
+        ADD     r2,r2,#1                    @ Increment the scheduled count
+        STR     r2,[r0, #0x1c]              @ Store new scheduled count
+
+    @ Check for time slice option. 
+@    if (thread -> tc_cur_time_slice)
+@    {
+        CMP     r3,#0                       @ Is there a time slice?
+        BEQ     TCT_No_Start_TS_1           @ If 0, there is no time slice
+
+        @ Start a time slice.
+@        TMD_Time_Slice =        thread -> tc_cur_time_slice;
+@        TMD_Time_Slice_State =  0;
+
+        LDR     r2,Time_Slice               @ Pickup address of TMD_Time_Slice
+        LDR     r1,Slice_State              @ Pickup address of 
+                                            @ TMD_Time_Slice_State
+        STR     r3,[r2, #0]                 @ Setup the time slice
+        MOV     r2,#0                       @ Build active state flag
+        STR     r2,[r1,#0]                  @ Set the active flag
+@    }
+TCT_No_Start_TS_1:
+#ifdef INCLUDE_PROVIEW
+@    Nucleus ProView Hook
+
+        STR     r0,[r13, #-4]!              @ Save r0 on the stack
+        BL      _NU_Schedule_Task_Hook      @ Branch to RTView
+        LDR     r0,[r13], #4                @ Recover return address
+#endif
+
+
+    @ Pickup the stack pointer and resume the thread.
+@    REG_Stack_Ptr =  thread -> tc_stack_pointer;
+
+        LDR     r13,[r0, #0x2c]             @ Switch to thread's stack pointer
+
+@ Pop off the saved information associated with the thread. After we
+@ determine which type of stack is present.  A 1 on the top of the 
+@ stack indicates an interrupt stack, while a 0 on the top of the
+@ stack indicates a solicited type of stack.
+
+@ Remember that the interrupt level that is restored must represent
+@ the interrupt level in TCD_Interrupt_Level.
+
+        LDR     r1,[r13], #4                @ Pop off the stack type 
+        CMP     r1,#1                       @ See if it is an interrupt stack
+        BEQ     TCT_Interrupt_Resume        @ If so, an interrupt resume of
+                                            @ thread is required
+        LDR     r1, Int_Level               @ Pickup address of interrupt 
+                                            @ lockout
+        MRS     r0,CPSR                     @ Pickup current CPSR
+        BIC     r0,r0,#LOCK_MSK             @ Clear lockout mask
+
+        BIC     r0,r0,#0x80000000
+
+
+        LDR     r2,[r1, #0]                 @ Pickup interrupt lockout mask
+        ORR     r0,r0,r2                    @ Build new interrupt lockout mask
+#if 1	/* was .if THUMB */
+        LDR     r2,[r13], #4                @ Pop off the state mask
+        ORR     r0,r0,r2                    @ Set appropriate state 
+#endif
+        MSR     SPSR,r0                     @ Place it into the SPSR 
+        LDMIA   r13!,{r4-r12,r15}^          @ A solicited return is required.  
+                                            @ This type of return only 
+                                            @ recovers r4-r13 & r15
+TCT_Interrupt_Resume:
+        LDR     r0,[r13], #4                @ Pop off the CPSR
+        LDR     r1,Int_Level                @ Pickup address of interrupt 
+                                            @ lockout
+        BIC     r0,r0,#LOCK_MSK             @ Clear lockout mask
+        LDR     r2,[r1, #0]                 @ Pickup interrupt lockout mask
+        ORR     r0,r0,r2                    @ Build new interrupt lockout mask
+        MSR     SPSR,r0                     @ Place it into the SPSR 
+        LDMIA   r13,{r0-r15}^               @ Recover all registers and resume
+                                            @ at point of interrupt
+@}
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *      TCT_Control_To_System                                            
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function returns control from a thread to the system.  Note 
+ *      that this service is called in a solicited manner, i.e. it is    
+ *      not called from an interrupt thread.  Registers required by the  
+ *      compiler to be preserved across function boundaries are saved by 
+ *      this routine.  Note that this is usually a sub-set of the total  
+ *      number of available registers.                                   
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      Other Components                                                 
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      TCT_Schedule                        Schedule the next thread     
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *      C. Meredith     03-01-1994      Corrected problem in time-slice  
+ *                                        reset logic, resulting in      
+ *                                        version 1.1                    
+ *      D. Lamie        03-18-1994      Verified version 1.1             
+ *                                                                       
+ ************************************************************************
+ */
+
+@VOID  TCT_Control_To_System(void)
+@{
+
+	.globl  TCT_Control_To_System
+TCT_Control_To_System:
+
+    @ Lockout interrupts. 
+
+        MRS     r0,CPSR                     @ Pickup current CPSR
+        ORR     r0,r0,#LOCKOUT              @ Build interrupt lockout value
+        MSR     CPSR,r0                     @ Lockout interrupts
+
+    @ Save a minimal context of the thread. 
+
+        STMDB   r13!,{r4-r12,r14}           @ Save minimal context of thread on
+                                            @ the current stack
+#if 1	/* was .if THUMB */
+        MOV     r2,r14                      @ Determine what state the caller
+        MOV     r2,r2,LSL #31               @ was in and build an
+        MOV     r2,r2,LSR #26               @ appropriate state mask
+        STR     r2,[r13, #-4]!              @ Place it on the stack
+#endif
+
+        MOV     r2,#0                       @ Build solicited stack type value
+                                            @ and NU_NULL value
+        STR     r2,[r13, #-4]!              @ Place it on the top of the stack
+
+    @ Setup a pointer to the thread control block. 
+@    REG_Thread_Ptr =  (TC_TCB *) TCD_Current_Thread;
+
+        LDR     r1,Current_Thread           @ Pickup current thread ptr address
+        LDR     r0,[r1, #0]                 @ Pickup current thread pointer
+
+    @ Clear the current thread control block pointer. 
+@    TCD_Current_Thread =  NU_NULL;
+
+        LDR     r3,Slice_State              @ Pickup time slice state address
+        STR     r2,[r1, #0]                 @ Set current thread pointer to 
+                                            @ NU_NULL
+
+@ Check to see if a time slice is active.  If so, copy the original time
+@ slice into the current time slice field of the task's control block.
+@    if (TMD_Time_Slice_State == 0)
+@    {
+        LDR     r1,[r3, #0]                 @ Pickup time slice state flag
+        CMP     r1,#0                       @ Compare with active value
+        BNE     TCT_No_Stop_TS_1            @ If non-active, don't disable
+
+    
+    @ Insure that the next time the task runs it gets a fresh time 
+    @ slice. 
+@       REG_Thread_Ptr -> tc_cur_time_slice =  REG_Thread_Ptr -> tc_time_slice;
+
+        LDR     r1,[r0, #0x40]              @ Pickup original time slice
+
+        @ Clear any active time slice by setting the state to NOT_ACTIVE. 
+@        TMD_Time_Slice_State =  1;
+
+        MOV     r2,#1                       @ Build disable value
+        STR     r2,[r3, #0]                 @ Disable time slice
+        STR     r1,[r0, #0x20]              @ Reset current time slice
+@    }
+TCT_No_Stop_TS_1:
+
+     @ Save off the current stack pointer in the control block. 
+@    REG_Thread_Ptr -> tc_stack_pointer =  (VOID *) REG_Stack_Ptr;
+
+        STR     r13,[r0, #0x2c]             @ Save the thread's stack pointer
+
+     @ Clear the task's current protection. 
+@    (REG_Thread_Ptr -> tc_current_protect) -> tc_tcb_pointer =  NU_NULL;
+@    REG_Thread_Ptr -> tc_current_protect =  NU_NULL;
+
+        LDR     r1,[r0, #0x38]              @ Pickup current thread pointer
+        MOV     r2,#0                       @ Build NU_NULL value
+        STR     r2,[r0, #0x38]              @ Clear the protect pointer field
+        STR     r2,[r1, #0]                 @ Release the actual protection
+
+    @ Switch to the system stack. 
+@    REG_Stack_Ptr =  TCD_System_Stack;
+
+        LDR     r1, System_Stack            @ Pickup address of stack pointer
+        LDR     r2, System_Limit            @ Pickup address of stack limit ptr
+        LDR     r13,[r1, #0]                @ Switch to system stack
+        LDR     r10,[r2, #0]                @ Setup system stack limit
+
+    @ Finished, return to the scheduling loop. 
+
+        B       TCT_Schedule                @ Return to scheduling loop
+@}
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *      TCT_Signal_Exit                                                  
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function exits from a signal handler.  The primary purpose  
+ *      of this function is to clear the scheduler protection and switch 
+ *      the stack pointer back to the normal task's stack pointer.       
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      TCC_Signal_Shell                    Signal handling shell func   
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      TCT_Schedule                        Scheduler                    
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *      C. Meredith     03-01-1994      Corrected problem in time-slice  
+ *                                        reset logic, resulting in      
+ *                                        version 1.1                    
+ *      D. Lamie        03-18-1994      Verified version 1.1             
+ *                                                                       
+ ************************************************************************
+ */
+
+@VOID  TCT_Signal_Exit(void)
+@{
+
+	.globl  TCT_Signal_Exit
+TCT_Signal_Exit:
+
+    @ Lockout interrupts. 
+
+        MRS     r3,CPSR                     @ Pickup current CPSR
+        ORR     r3,r3,#LOCKOUT              @ Build lockout value
+        MSR     CPSR,r3                     @ Lockout interrupts
+
+    @ Setup a pointer to the thread control block. 
+@    REG_Thread_Ptr =  (TC_TCB *) TCD_Current_Thread;
+
+        LDR     r1,Current_Thread           @ Pickup address of thread pointer
+        MOV     r2,#0                       @ Build NU_NULL value
+        LDR     r0,[r1,#0]                  @ Pickup current thread pointer
+
+    @ Clear the current thread control block. 
+@    TCD_Current_Thread =  NU_NULL;
+
+        LDR     r3,Slice_State              @ Pickup time slice state address
+        STR     r2,[r1, #0]                 @ Clear current thread pointer
+
+    @ Check to see if a time slice is active.  If so, copy the original time
+    @ slice into the current time slice field of the task's control block.
+@    if (TMD_Time_Slice_State == 0)
+@    {
+
+        LDR     r1,[r3, #0]                 @ Pickup time slice state flag
+        CMP     r1,#0                       @ Compare with active value
+        BNE     TCT_No_Stop_TS_2            @ If non-active, don't disable
+
+        @ Insure that the next time the task runs it gets a fresh time 
+        @ slice. 
+@       REG_Thread_Ptr -> tc_cur_time_slice =  REG_Thread_Ptr -> tc_time_slice;
+
+        LDR     r1,[r0, #0x40]              @ Pickup original time slice
+
+        @ Clear any active time slice by setting the state to NOT_ACTIVE. 
+@        TMD_Time_Slice_State =  1;
+
+        MOV     r2,#1                       @ Build disable value
+        STR     r2,[r3, #0]                 @ Disable time slice
+        STR     r1,[r0, #0x20]              @ Reset current time slice
+@    }
+TCT_No_Stop_TS_2:
+
+    @ Switch back to the saved stack.  The saved stack pointer was saved
+    @ before the signal frame was built. 
+@    REG_Thread_Ptr -> tc_stack_pointer =  
+@                                REG_Thread_Ptr -> tc_saved_stack_ptr;
+
+        LDR     r1,[r0, #0x3c]              @ Pickup saved stack pointer
+        STR     r1,[r0, #0x2c]              @ Place in current stack pointer
+
+    @ Clear the task's current protection. 
+@    (REG_Thread_Ptr -> tc_current_protect) -> tc_tcb_pointer =  NU_NULL;
+@    REG_Thread_Ptr -> tc_current_protect =  NU_NULL;
+
+        LDR     r1,[r0, #0x38]              @ Pickup current thread pointer
+        MOV     r2,#0                       @ Build NU_NULL value
+        STR     r2,[r0, #0x38]              @ Clear the protect pointer field
+        STR     r2,[r1, #0]                 @ Release the actual protection
+
+    @ Switch to the system stack. 
+@    REG_Stack_Ptr =  (BYTE_PTR) TCD_System_Stack;
+
+        LDR     r1, System_Stack            @ Pickup address of stack pointer
+        LDR     r2, System_Limit            @ Pickup address of stack limit ptr
+        LDR     r13,[r1, #0]                @ Switch to system stack
+        LDR     r10,[r2, #0]                @ Setup system stack limit
+
+    @ Finished, return to the scheduling loop. 
+
+        B       TCT_Schedule                @ Return to scheduling loop
+@}
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *      TCT_Current_Thread                                               
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function returns the current thread pointer.                
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      Application                                                      
+ *      System Components                                                
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      Pointer to current thread                                        
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *                                                                       
+ ************************************************************************
+ */
+
+@VOID  *TCT_Current_Thread(void)
+@{
+
+	.globl  TCT_Current_Thread
+TCT_Current_Thread:
+
+    @ Return the current thread pointer. 
+@    return(TCD_Current_Thread);
+
+        LDR     r0, Current_Thread          @ Pickup address of thread pointer
+        LDR     r0,[r0, #0]                 @ Pickup current thread pointer
+
+        BX      r14                         @ Return to caller
+
+@}
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *      TCT_Set_Execute_Task                                             
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function sets the current task to execute variable under    
+ *      protection against interrupts.                                   
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      TCC Scheduling Routines                                          
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      task                                Pointer to task control block
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      TCD_Execute_Task                    Modified variable            
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *                                                                       
+ ************************************************************************
+ */
+
+@VOID  TCT_Set_Execute_Task(TC_TCB *task)
+@{
+
+	.globl  TCT_Set_Execute_Task
+TCT_Set_Execute_Task:
+
+    @ Now setup the TCD_Execute_Task pointer. 
+@    TCD_Execute_Task =  task;
+
+        LDR     r1, Execute_Task            @ Pickup execute task ptr address
+        STR     r0,[r1,#0]                  @ Setup new task to execute
+
+        BX      r14                         @ Return to caller
+
+@}
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *      TCT_Protect                                                      
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function protects against multiple thread access.           
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      Application                                                      
+ *      System Components                                                
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      protect                            Pointer to protection block   
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *                                                                       
+ ************************************************************************
+ */
+
+@VOID  TCT_Protect(TC_PROTECT *protect)
+@{
+
+	.globl  TCT_Protect
+TCT_Protect:
+
+    @ Determine if the caller is in a task or HISR thread. 
+@    if (TCD_Current_Thread)
+@    {
+
+        LDR     r1,Current_Thread           @ Pickup current thread ptr address
+        LDR     r3,[r1, #0]                 @ Pickup current thread pointer
+        CMP     r3,#0                       @ Check to see if it is non-NULL
+        BEQ     TCT_Skip_Protect            @ If NULL, skip protection
+
+        @ Lockout interrupts. 
+
+        MRS     r1,CPSR                     @ Pickup current CPSR
+        ORR     r1,r1,#LOCKOUT              @ Place lockout value in
+        MSR     CPSR,r1                     @ Lockout interrupts
+
+        @ Wait until the protect structure is available. 
+@        while (protect -> tc_tcb_pointer != NU_NULL)
+@        {
+
+TCT_Protect_Loop:
+        LDR     r1,[r0, #0]                 @ Pickup protection owner field
+        CMP     r1,#0                       @ Is there any protection?
+        BEQ     TCT_Protect_Available       @ If NU_NULL, no current protection
+
+        @ Protection structure is not available. 
+
+        @ Indicate that another thread is waiting. 
+@         protect -> tc_thread_waiting =  1;
+
+        MOV     r2,#1                       @ Build thread waiting flag
+        STR     r2,[r0, #4]                 @ Set waiting field
+
+        @ Directly schedule the thread waiting. 
+@       TCT_Schedule_Protected(protect -> tc_tcb_pointer);
+
+        STR     r0,[r13, #-4]!              @ Save r0 on the stack
+        STR     r14,[r13, #-4]!             @ Save r14 on the stack
+        MOV     r0,r3                       @ Place current thread into r0
+        BL      TCT_Schedule_Protected      @ Call routine to schedule the 
+                                            @ owner of the thread
+
+        LDR     r14,[r13], #4               @ Recover saved r14
+        LDR     r0,[r13], #4                @ Recover saved r0
+
+        @ Lockout interrupts. 
+
+        LDR     r1,Current_Thread           @ Pickup current thread ptr address
+        LDR     r3,[r1, #0]                 @ Pickup current thread pointer
+        MRS     r1,CPSR                     @ Pickup current CPSR
+        ORR     r1,r1,#LOCKOUT              @ Place lockout value in
+        MSR     CPSR,r1                     @ Lockout interrupts
+        B       TCT_Protect_Loop            @ Examine protect flags again
+@        }
+TCT_Protect_Available:
+
+        @ Protection structure is available. 
+    
+        @ Indicate that this thread owns the protection. 
+@        protect -> tc_tcb_pointer =  TCD_Current_Thread;
+
+        STR     r3,[r0, #0]                 @ Indicate calling thread owns this
+                                            @ protection
+
+        @ Clear the thread waiting flag. 
+@        protect -> tc_thread_waiting =  0;
+
+        MOV     r2,#0                       @ Clear value
+        STR     r2,[r0, #4]                 @ Clear the thread waiting flag
+
+@ Save the protection pointer in the thread's control block.  Note 
+@ that both task and HISR threads share the same control block 
+@ format. 
+@        REG_Thread_Ptr =  (TC_TCB *) TCD_Current_Thread;
+@        REG_Thread_Ptr -> tc_current_protect =  protect;
+
+        STR     r0,[r3, #0x38]              @ Setup current protection
+
+        @ Restore interrupts. 
+
+        LDR     r2,Int_Level                @ Pickup address of interrupt level
+        MRS     r1,CPSR                     @ Pickup current CPSR
+        LDR     r3,[r2, #0]                 @ Pickup interrupt lockout level
+        BIC     r1,r1,#LOCK_MSK             @ Clear lockout bits
+        ORR     r1,r1,r3                    @ Build new interrupt lockout
+        MSR     CPSR,r1                     @ Setup CPSR appropriately
+@    }
+
+TCT_Skip_Protect:
+
+        BX      r14                         @ Return to caller
+
+@}
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *      TCT_Unprotect                                                    
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function releases protection of the currently active        
+ *      thread.  If the caller is not an active thread, then this        
+ *      request is ignored.                                              
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      Application                                                      
+ *      System Components                                                
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *                                                                       
+ ************************************************************************
+ */
+
+@VOID  TCT_Unprotect(void)
+@{
+
+	.globl  TCT_Unprotect
+TCT_Unprotect:
+
+
+    @ Determine if the caller is in a task or HISR thread. 
+@    if (TCD_Current_Thread)
+@    {
+
+        LDR     r1,Current_Thread           @ Pickup current thread ptr address
+        LDR     r3,[r1, #0]                 @ Pickup current thread pointer
+        CMP     r3,#0                       @ Check to see if it is non-NULL
+        BEQ     TCT_Skip_Unprotect          @ If NULL, skip unprotection
+
+        @ Setup a thread control block pointer. 
+@        REG_Thread_Ptr =  (TC_TCB *) TCD_Current_Thread;
+
+        @ Determine if there is a currently active protection. 
+@        if (REG_Thread_Ptr -> tc_current_protect)
+@        {
+
+        LDR     r0,[r3, #0x38]              @ Pickup current protect field
+        CMP     r0,#0                       @ Is there a protection in force?
+        BEQ     TCT_Skip_Unprotect          @ If not, nothing is protected
+
+        @ Lockout interrupts. 
+
+        MRS     r1,CPSR                     @ Pickup current CPSR
+        ORR     r1,r1,#LOCKOUT              @ Place lockout value in
+        MSR     CPSR,r1                     @ Lockout interrupts
+
+        @ Yes, this thread still has this protection structure. 
+@            REG_Protect_Ptr =  REG_Thread_Ptr -> tc_current_protect;
+
+        @ Is there a higher priority thread waiting for the protection
+        @ structure? 
+@            if (REG_Protect_Ptr -> tc_thread_waiting)
+
+        LDR     r2,[r0, #4]                 @ Pickup thread waiting flag
+        CMP     r2,#0                       @ Are there any threads waiting?
+        BEQ     TCT_Not_Waiting_Unpr        @ If not, just release protection
+
+@                Transfer control to the system.  Note that this 
+@                   automatically clears the current protection and it returns
+@                   to the caller of this routine instead of this routine. 
+@                TCT_Control_To_System();
+
+        B       TCT_Control_To_System       @ Return control to the system
+
+@            else
+@            {
+TCT_Not_Waiting_Unpr:
+
+        @ Clear the protection. 
+@                REG_Thread_Ptr -> tc_current_protect =  NU_NULL;
+@                REG_Protect_Ptr -> tc_tcb_pointer =  NU_NULL;
+
+        MOV     r2,#0                       @ Build NU_NULL value
+        STR     r2,[r0, #0]                 @ Release the protection
+        STR     r2,[r3, #0x38]              @ Clear protection pointer in the
+                                            @ control block
+
+@            }
+
+TCT_Not_Protected:
+        @ Restore interrupts again. 
+
+        LDR     r2,Int_Level                @ Pickup address of interrupt level
+        MRS     r1,CPSR                     @ Pickup current CPSR
+        LDR     r3,[r2, #0]                 @ Pickup interrupt lockout level
+        BIC     r1,r1,#LOCK_MSK             @ Clear lockout bits
+        ORR     r1,r1,r3                    @ Build new interrupt lockout
+        MSR     CPSR,r1                     @ Setup CPSR appropriately
+
+@        }
+@    }
+TCT_Skip_Unprotect:
+
+        BX      r14                         @ Return to caller
+
+@}
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *      TCT_Unprotect_Specific                                           
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function releases a specific protection structure.          
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      Application                                                      
+ *      System Components                                                
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      protect                            Pointer to protection block   
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *      C. Meredith     03-01-1994      Corrected problem in time-slice  
+ *                                        reset logic, corrected bug     
+ *                                        using protect ptr, resulting   
+ *                                        in version 1.1                 
+ *      D. Lamie        03-18-1994      Verified version 1.1             
+ *                                                                       
+ ************************************************************************
+ */
+
+@VOID  Specific(TC_PROTECT *protect)
+@{
+
+	.globl  TCT_Unprotect_Specific
+TCT_Unprotect_Specific:
+
+    @ Determine if the caller is in a task or HISR thread. 
+@    if (TCD_Current_Thread)
+@    {
+
+        LDR     r1,Current_Thread           @ Pickup current thread ptr address
+        LDR     r3,[r1, #0]                 @ Pickup current thread pointer
+        CMP     r3,#0                       @ Check to see if it is non-NULL
+        BEQ     TCT_Skip_Unprot_Spec        @ If NULL, skip unprotect specific
+
+        @ Lockout interrupts. 
+
+        MRS     r1,CPSR                     @ Pickup current CPSR
+        ORR     r1,r1,#LOCKOUT              @ Place lockout value in
+        MSR     CPSR,r1                     @ Lockout interrupts
+
+        @ Clear the protection pointer. 
+@        protect -> tc_tcb_pointer =  NU_NULL;
+
+        MOV     r2,#0                       @ Build NU_NULL value
+        STR     r2,[r0, #0]                 @ Clear protection ownership
+
+        @ Determine if a thread is waiting. 
+@        if (protect -> tc_thread_waiting)
+@        {
+
+        LDR     r1,[r0, #4]                 @ Pickup the waiting field
+        CMP     r1,#0                       @ Is there another thread waiting?
+        BEQ     TCT_Not_Waiting_Unspec      @ No, restore interrupts and return
+
+        @ A higher-priority thread is waiting. 
+
+        @ Save a minimal context of the thread. 
+
+        STMDB   r13!,{r4-r12,r14}           @ Save minimal context of thread on
+                                            @ the current stack
+
+#if 1	/* was .if THUMB */
+        MOV     r2,r14                      @ Determine what state the caller
+        MOV     r2,r2,LSL #31               @ was in and build an
+        MOV     r2,r2,LSR #26               @ appropriate state mask
+        STR     r2,[r13, #-4]!              @ Place it on the stack
+#endif
+
+        MOV     r2,#0                       @ Build solicited stack type value
+                                            @ and NU_NULL value
+        STR     r2,[r13, #-4]!              @ Place it on the top of the stack
+
+        @ Setup a pointer to the thread control block. 
+@            REG_Thread_Ptr =  (TC_TCB *) TCD_Current_Thread;
+
+        LDR     r1,Current_Thread           @ Pickup current thread ptr address
+        LDR     r0,[r1, #0]                 @ Pickup current thread pointer
+
+        @ Clear the current thread control block pointer. 
+@            TCD_Current_Thread =  NU_NULL;
+
+        LDR     r3,Slice_State              @ Pickup time slice state address
+        STR     r2,[r1, #0]                 @ Set current thread pointer to 
+                                            @ NU_NULL
+
+        @ Check to see if a time slice is active.  If so, copy the 
+        @ original time slice into the current time slice field of the 
+        @ thread's control block.
+@            if (TMD_Time_Slice_State == 0)
+@            {
+
+        LDR     r1,[r3, #0]                 @ Pickup time slice state flag
+        CMP     r1,#0                       @ Compare with active value
+        BNE     TCT_No_Stop_TS_3            @ If non-active, don't disable
+
+        @ Insure that the next time the task runs it gets a fresh time
+        @ slice. 
+@                REG_Thread_Ptr -> tc_cur_time_slice =  
+@                                        REG_Thread_Ptr -> tc_time_slice;
+
+        LDR     r1,[r0, #0x40]              @ Pickup original time slice
+
+        @ Clear any active time slice by setting the state to 
+        @ NOT_ACTIVE. 
+@                TMD_Time_Slice_State =  1;
+
+        MOV     r2,#1                       @ Build disable value
+        STR     r2,[r3, #0]                 @ Disable time slice
+        STR     r1,[r0, #0x20]              @ Reset current time slice
+@            }
+
+TCT_No_Stop_TS_3:
+
+        @ Save off the current stack pointer in the control block. 
+@            REG_Thread_Ptr -> tc_stack_pointer =  (VOID *) REG_Stack_Ptr;
+
+        STR     r13,[r0, #0x2c]             @ Save the thread's stack pointer
+
+        @ Switch to the system stack. 
+@            REG_Stack_Ptr =  TCD_System_Stack;
+
+        LDR     r1,System_Stack             @ Pickup address of stack pointer
+        LDR     r2,System_Limit             @ Pickup address of stack limit ptr
+        LDR     r13,[r1, #0]                @ Switch to system stack
+        LDR     r10,[r2, #0]                @ Setup system stack limit
+
+        @ Finished, return to the scheduling loop. 
+
+        B       TCT_Schedule                @ Return to scheduling loop
+
+@        }
+@        else
+@        {
+TCT_Not_Waiting_Unspec:
+
+        @ No higher-priority thread is waiting. 
+
+@            Restore interrupts. 
+
+        LDR     r2,Int_Level                @ Pickup address of interrupt level
+        MRS     r1,CPSR                     @ Pickup current CPSR
+        LDR     r3,[r2, #0]                 @ Pickup interrupt lockout level
+        BIC     r1,r1,#LOCK_MSK             @ Clear lockout bits
+        ORR     r1,r1,r3                    @ Build new interrupt lockout
+        MSR     CPSR,r1                     @ Setup CPSR appropriately
+
+@        }
+@    }
+
+TCT_Skip_Unprot_Spec:
+
+        BX      r14                         @ Return to caller
+
+@}
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *      TCT_Set_Current_Protect                                          
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function sets the current protection field of the current   
+ *      thread's control block to the specified protection pointer.      
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      TCC_Resume_Task                    Resume task function          
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      protect                            Pointer to protection block   
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *                                                                       
+ ************************************************************************
+ */
+
+@VOID  TCT_Set_Current_Protect(TC_PROTECT *protect)
+@{
+
+	.globl  TCT_Set_Current_Protect
+TCT_Set_Current_Protect:
+
+    @ Determine if the caller is in a task or HISR thread. 
+@    if (TCD_Current_Thread)
+@    {
+
+        LDR     r1,Current_Thread           @ Pickup current thread ptr address
+        LDR     r3,[r1, #0]                 @ Pickup current thread pointer
+        CMP     r3,#0                       @ Check to see if a thread is 
+                                            @ active
+
+        @ Point at the current thread control block. 
+@        REG_Thread_Ptr =  (TC_TCB *) TCD_Current_Thread;
+
+        @ Modify the current protection. 
+@        REG_Thread_Ptr -> tc_current_protect =  protect;
+
+        STRNE   r0,[r3, #0x38]              @ Setup new protection
+@    }
+
+
+        BX      r14                         @ Return to caller
+
+@}
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *      TCT_Protect_Switch                                               
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function waits until a specific task no longer has any      
+ *      protection associated with it.  This is necessary since task's   
+ *      cannot be suspended or terminated unless they have released all  
+ *      of their protection.                                             
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      System Components                                                
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      thread                             Pointer to thread control blk 
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *                                                                       
+ ************************************************************************
+ */
+
+@VOID  TCT_Protect_Switch(VOID *thread)
+@{
+
+	.globl  TCT_Protect_Switch
+TCT_Protect_Switch:
+
+        @ Lockout interrupts. 
+
+        MRS     r1,CPSR                     @ Pickup current CPSR
+        ORR     r1,r1,#LOCKOUT              @ Place lockout value in
+        MSR     CPSR,r1                     @ Lockout interrupts
+
+@    REG_Thread_Ptr =  (TC_TCB *) thread;
+
+    @ Wait until the specified task has no protection associated with it. 
+@    while (REG_Thread_Ptr -> tc_current_protect)
+@    {
+
+        LDR     r1,[r0, #0x38]              @ Pickup protection of specified
+                                            @ thread
+        CMP     r1,#0                       @ Does the specified thread have
+                                            @ an active protection?
+        BEQ     TCT_Switch_Done             @ If not, protect switch is done
+
+        @ Let the task run again in an attempt to clear its protection. 
+
+        @ Indicate that a higher priority thread is waiting. 
+@        (REG_Thread_Ptr -> tc_current_protect) -> tc_thread_waiting =  1;
+
+        MOV     r2,#1                       @ Build waiting flag value
+        STR     r2,[r1, #4]                 @ Set waiting flag of the 
+                                            @ protection owned by the other
+                                            @ thread
+
+        @ Directly schedule the thread waiting. 
+@        TCT_Schedule_Protected((REG_Thread_Ptr -> tc_current_protect)  
+@                                                        -> tc_tcb_pointer);
+
+        LDR     r2,Current_Thread           @ Pickup current thread ptr address
+        STR     r0,[r13, #-4]!              @ Save r0 on the stack
+        STR     r14,[r13, #-4]!             @ Save r14 on the stack
+        MOV     r1,r0                       @ Move new thread into r1
+        LDR     r0,[r2, #0]                 @ Pickup current thread pointer
+        BL      TCT_Schedule_Protected      @ Call routine to schedule the 
+                                            @ owner of the thread
+
+        LDR     r14,[r13], #4               @ Recover saved r14
+        LDR     r0,[r13], #4                @ Recover saved r0
+
+        @ Lockout interrupts. 
+
+        B       TCT_Protect_Switch          @ Branch to top of routine and 
+                                            @ start over
+@    }
+TCT_Switch_Done:
+
+        @ Restore interrupts. 
+
+        LDR     r2,Int_Level                @ Pickup address of interrupt level
+        MRS     r1,CPSR                     @ Pickup current CPSR
+        LDR     r3,[r2, #0]                 @ Pickup interrupt lockout level
+        BIC     r1,r1,#LOCK_MSK             @ Clear lockout bits
+        ORR     r1,r1,r3                    @ Build new interrupt lockout
+        MSR     CPSR,r1                     @ Setup CPSR appropriately
+
+
+        BX      r14                         @ Return to caller
+
+@}
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *      TCT_Schedule_Protected                                           
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function saves the minimal context of the thread and then   
+ *      directly schedules the thread that has protection over the       
+ *      the thread that called this routine.                             
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      TCT_Protect                                                      
+ *      TCT_Protect_Switch                                               
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      TCT_Control_To_Thread               Transfer control to protected
+ *                                              thread                   
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *      C. Meredith     03-01-1994      Corrected problem in time-slice  
+ *                                        reset logic, resulting in      
+ *                                        version 1.1                    
+ *      D. Lamie        03-18-1994      Verified version 1.1             
+ *                                                                       
+ ************************************************************************
+ */
+
+@VOID  TCT_Schedule_Protected(VOID *thread)
+@{
+
+	.globl	TCT_Schedule_Protected
+TCT_Schedule_Protected:
+
+    @ Interrupts are already locked out by the caller. 
+
+    @ Save minimal context required by the system. 
+
+        STMDB   r13!,{r4-r12,r14}           @ Save minimal context of thread on
+                                            @ the current stack
+
+#if 1	/* was .if THUMB */
+        MOV     r2,r14                      @ Determine what state the caller
+        MOV     r2,r2,LSL #31               @ was in and build an
+        MOV     r2,r2,LSR #26               @ appropriate state mask
+        STR     r2,[r13, #-4]!              @ Place it on the stack
+#endif
+
+        MOV     r2,#0                       @ Build solicited stack type value
+                                            @ and NU_NULL value
+        STR     r2,[r13, #-4]!              @ Place it on the top of the stack
+        MOV     r4,r1                       @ Save thread to schedule
+
+    @ Setup a pointer to the thread control block. 
+@    REG_Thread_Ptr =  (TC_TCB *) TCD_Current_Thread;
+
+        LDR     r1,Current_Thread           @ Pickup current thread ptr address
+
+    @ Clear the current thread control block. 
+@    TCD_Current_Thread =  NU_NULL;
+
+        LDR     r3,Slice_State              @ Pickup time slice state address
+        STR     r2,[r1, #0]                 @ Set current thread pointer to 
+                                            @ NU_NULL
+
+    @ Check to see if a time slice is active.  If so, copy the original time
+    @ slice into the current time slice field of the task's control block.
+@    if (TMD_Time_Slice_State == 0)
+@    {
+
+        LDR     r1,[r3, #0]                 @ Pickup time slice state flag
+        CMP     r1,#0                       @ Compare with active value
+        BNE     TCT_No_Stop_TS_4            @ If non-active, don't disable
+
+    @ Insure that the next time the task runs it gets a fresh time 
+    @ slice. 
+@       REG_Thread_Ptr -> tc_cur_time_slice =  REG_Thread_Ptr -> tc_time_slice;
+
+        LDR     r1,[r0, #0x40]              @ Pickup original time slice
+
+    @ Clear any active time slice by setting the state to NOT_ACTIVE. 
+@        TMD_Time_Slice_State =  1;
+
+        MOV     r2,#1                       @ Build disable value
+        STR     r2,[r3, #0]                 @ Disable time slice
+        STR     r1,[r0, #0x20]              @ Reset current time slice
+
+@    }
+TCT_No_Stop_TS_4:
+
+    @ Save off the current stack pointer in the control block. 
+@    REG_Thread_Ptr -> tc_stack_pointer =  (VOID *) REG_Stack_Ptr;
+
+        STR     r13,[r0, #0x2c]             @ Save the thread's stack pointer
+
+    @ Switch to the system stack. 
+@    TCD_System_Stack =  (VOID *) REG_Stack_Ptr;
+
+        LDR     r1,System_Stack             @ Pickup address of stack pointer
+        LDR     r2,System_Limit             @ Pickup address of stack limit ptr
+        LDR     r13,[r1, #0]                @ Switch to system stack
+        LDR     r10,[r2, #0]                @ Setup system stack limit
+
+    @ Transfer control to the specified thread directly.
+@    TCT_Control_To_Thread(thread);
+
+        LDR     r2,Int_Level                @ Pickup address of interrupt level
+        MRS     r1,CPSR                     @ Pickup current CPSR
+        LDR     r3,[r2, #0]                 @ Pickup interrupt lockout level
+        BIC     r1,r1,#LOCK_MSK             @ Clear lockout bits
+        ORR     r1,r1,r3                    @ Build new interrupt lockout
+        MOV     r0,r4                       @ Indicate thread to schedule
+        MSR     CPSR,r1                     @ Setup CPSR appropriately
+        ORR     r1,r1,#LOCKOUT              @ Build lockout value again
+        MSR     CPSR,r1                     @ Lockout interrupts again
+        B       TCT_Control_To_Thread       @ Schedule the thread indirectly
+@}
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *      TCT_Interrupt_Context_Save                                       
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function saves the interrupted thread's context.  Nested    
+ *      interrupts are also supported.  If a task or HISR thread was     
+ *      interrupted, the stack pointer is switched to the system stack   
+ *      after the context is saved.                                      
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      Application ISRs                    Assembly language ISRs       
+ *      INT_Interrupt_Shell                 Interrupt handler shell      
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      vector                              Interrupt's vector number    
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *      D. Driscoll     01-04-2002      Released version 1.13.3.         
+ *                                      Updated to handle nested /       
+ *                                      prioritized IRQs                 
+ ************************************************************************
+ */
+
+@VOID  TCT_Interrupt_Context_Save(INT vector)
+@{
+
+	.globl  TCT_Interrupt_Context_Save
+TCT_Interrupt_Context_Save:
+        @ Determine if this is a nested interrupt. 
+        LDR     r1,Int_Count                @ Pickup address of interrupt count
+        LDR     r2,[r1, #0]                 @ Pickup interrupt counter
+        ADD     r2,r2,#1                    @ Add 1 to interrupt counter
+        STR     r2,[r1, #0]                 @ Store new interrupt counter value
+        CMP     r2,#1                       @ Is it nested?
+        BEQ     TCT_Not_Nested_Save         @ No
+
+@ Nested interrupt.  Save complete context on the current stack. 
+TCT_Nested_Save:
+
+/* No longer needed in the FreeCalypso version, as we can use r0 instead. */
+#if 0
+@       1.  Save another register on the exception stack so we have enough to work with
+        STMDB   r13!,{r5}
+#endif
+
+@       2.  Save the necessary exception registers into r1-r3
+        MOV     r1,r13                      @ Put the exception r13 into r1
+        MOV     r2,r14                      @ Move the return address for the caller
+                                            @  of this function into r2
+        MRS     r3,spsr                     @ Put the exception spsr into r3
+
+@       3.  Adjust the exception stack pointer for future exceptions
+        ADD     r13,r13,#20                 @ r13 reset to pre-interrupt value
+
+@       4.  Switch CPU modes to save context on system stack
+        MRS     r0,CPSR                     @ Pickup the current CPSR
+        BIC     r0,r0,#MODE_MASK            @ Clear the mode bits
+        
+        ORR     r0,r0,#SUP_MODE             @ Change to supervisor mode (SVD)
+        
+        MSR     CPSR,r0                     @ Switch modes (IRQ->SVC)
+
+@       5.  Store the SVC r13 into r5 so the r13 can be saved as is.
+@	FreeCalyspo: using r0 instead
+        MOV     r0,r13
+
+@       6.  Save the exception return address on the stack (r15).
+        STMDB   r0!,{r4}
+
+@       7.  Save r5-r14 on stack (used to be r6-r14)
+        STMDB   r0!,{r5-r14}
+
+@       8.  Switch back to using r13 now that the original r13 has been saved.
+        MOV     r13,r0
+
+/* no longer relevant */
+#if 0
+@       9.  Get r5 and exception enable registers off of exception stack and
+@              save r5 (stored in r4) back to the system stack.
+        LDMIA   r1!,{r4-r5}
+        STMDB   r13!,{r4}
+        MOV     r4,r5                       @ Put exception enable value into r4
+#endif
+
+@       10. Get the rest of the registers off the exception stack and
+@              save them onto the system stack.
+        LDMIA   r1!,{r5-r8,r11}             @ Get r0-r4 off exception stack
+        STMDB   r13!,{r5-r8,r11}            @ Put r0-r4 on system stack
+
+/* no longer relevant */
+#if 0
+@       11. Store the exception enable value back on the exception stack.
+        STMDB   r1,{r4}
+#endif
+
+@       12. Save the SPSR on the system stack (CPSR)
+        STMDB   r13!,{r3}
+
+/* TI's approach to interrupt handling does not support re-enabling here */
+#if 0
+@       13. Re-enable interrupts
+        MRS     r1,CPSR
+        BIC     r1,r1,#(IRQ_BIT_OR_FIQ_BIT)
+        MSR     CPSR,r1
+#endif
+
+        BX      r2                          @ Return to calling ISR
+@    }
+@    else
+@    {
+TCT_Not_Nested_Save:
+
+        @ Determine if a thread was interrupted. 
+@       if (TCD_Current_Thread)
+@       {
+
+        LDR     r1,Current_Thread           @ Pickup current thread ptr address
+        LDR     r1,[r1, #0]                 @ Pickup the current thread pointer
+        CMP     r1,#0                       @ Is it NU_NULL?
+        BEQ     TCT_Idle_Context_Save       @ If no, no real save is necessary
+
+
+        @ Yes, a thread was interrupted.  Save complete context on the
+        @ thread's stack. 
+
+/* No longer needed in the FreeCalypso version, as we can use r0 instead. */
+#if 0
+@       1.  Save another register on the exception stack so we have enough to work with
+        STMDB   r13!,{r5}
+#endif
+
+@       2.  Save the necessary exception registers into r1-r3
+        MOV     r1,r13                      @ Put the exception r13 into r1
+        MOV     r2,r14                      @ Move the return address for the caller
+                                            @  of this function into r2
+        MRS     r3,spsr                     @ Put the exception spsr into r3
+
+@       3.  Adjust the exception stack pointer for future exceptions
+        ADD     r13,r13,#20                 @ r13 reset to pre-interrupt value
+
+@       4.  Switch CPU modes to save context on system stack
+        MRS     r0,CPSR                     @ Pickup the current CPSR
+        BIC     r0,r0,#MODE_MASK            @ Clear the mode bits
+        
+        ORR     r0,r0,#SUP_MODE             @ Change to supervisor mode (SVD)
+        
+        MSR     CPSR,r0                     @ Switch modes (IRQ->SVC)
+
+@       5.  Store the SVC r13 into r5 so the r13 can be saved as is.
+@	FreeCalyspo: using r0 instead
+        MOV     r0,r13
+
+@       6.  Save the exception return address on the stack (r15).
+        STMDB   r0!,{r4}
+
+@       7.  Save r5-r14 on stack (used to be r6-r14)
+        STMDB   r0!,{r5-r14}
+
+@       8.  Switch back to using r13 now that the original r13 has been saved.
+        MOV     r13,r0
+
+/* no longer relevant */
+#if 0
+@       9. Get r5 and exception enable registers off of exception stack and
+@          save r5 (stored in r4) back to the system stack.
+        LDMIA   r1!,{r4-r5}
+        STMDB   r13!,{r4}
+        MOV     r4,r5                       @ Put exception enable value into r4
+#endif
+
+@       10. Get the rest of the registers off the exception stack and
+@           save them onto the system stack.
+        LDMIA   r1!,{r5-r8,r11}             @ Get r0-r4 off exception stack
+        STMDB   r13!,{r5-r8,r11}            @ Put r0-r4 on system stack
+
+/* no longer relevant */
+#if 0
+@       11. Store the exception enable value back on the exception stack.
+        STMDB   r1,{r4}
+#endif
+
+@       12. Save the SPSR on the system stack (CPSR)
+        STMDB   r13!,{r3}
+
+@       13. Save stack type to the task stack (1=interrupt stack)
+        MOV     r1,#1                       @ Interrupt stack type
+        STMDB   r13!,{r1}
+
+        @ Save the thread's stack pointer in the control block. 
+@       REG_Thread_Ptr =  (TC_TCB *) TCD_Current_Thread
+@       REG_Thread_Ptr -> tc_stack_pointer =  (VOID *) REG_Stack_Ptr
+
+        LDR     r1,Current_Thread           @ Pickup current thread ptr address
+        LDR     r3,[r1, #0]                 @ Pickup current thread pointer
+        STR     r13,[r3, #TC_STACK_POINTER] @ Save stack pointer
+
+        @ Switch to the system stack. 
+@            REG_Stack_Ptr =  TCD_System_Stack
+
+        LDR     r1,System_Stack             @ Pickup address of stack pointer
+        LDR     r3,System_Limit             @ Pickup address of stack limit ptr
+        LDR     r13,[r1, #0]                @ Switch to system stack
+        LDR     r10,[r3, #0]                @ Setup system stack limit
+
+/* TI's approach to interrupt handling does not support re-enabling here */
+#if 0
+        @ Re-enable interrupts
+        MRS     r1,CPSR
+        BIC     r1,r1,#(IRQ_BIT_OR_FIQ_BIT)
+        MSR     CPSR,r1
+#endif
+ 
+@ Return to caller ISR. 
+
+        BX      r2                          @ Return to caller ISR
+
+@       }
+
+TCT_Idle_Context_Save:
+
+        MOV     r2,r14                      @ Save r14 in r2
+@       LDR     r3,[r13]                    @ Get exception enable value from stack
+        ADD     r13,r13,#20                 @ Adjust exception r13 for future interrupts
+@       STR     r3,[r13]                    @ Put exception enable value back on stack
+
+        MRS     r1,CPSR                     @ Pickup current CPSR
+        BIC     r1,r1,#MODE_MASK            @ Clear the current mode
+@       BIC     r1,r1,#(IRQ_BIT_OR_FIQ_BIT) @ Re-enable interrupts
+        
+        ORR     r1,r1,#SUP_MODE             @ Prepare to switch to supervisor
+                                            @   mode (SVC)
+        MSR     CPSR,r1                     @ Switch to supervisor mode (SVC)
+
+        BX      r2                          @ Return to caller ISR
+
+@    }
+@}
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *      TCT_Interrupt_Context_Restore                                    
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function restores the interrupt context if a nested         
+ *      interrupt condition is present.  Otherwise, this routine         
+ *      transfers control to the scheduling function.                    
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      Application ISRs                    Assembly language ISRs       
+ *      INT_Interrupt_Shell                 Interrupt handler shell      
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      TCT_Schedule                        Thread scheduling function   
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *      D. Driscoll     01-04-2002      Released version 1.13.3.         
+ *                                      Updated to handle nested /       
+ *                                      prioritized IRQs                 
+ *                                                                       
+ ************************************************************************
+ */
+
+@VOID  TCT_Interrupt_Context_Restore(void)
+@{
+
+	.globl  TCT_Interrupt_Context_Restore
+TCT_Interrupt_Context_Restore:
+    @ It is assumed that anything pushed on the stack by ISRs has been
+    @ removed upon entry into this routine. 
+
+    @ Decrement and check for nested interrupt conditions. 
+@    if (--TCD_Interrupt_Count)
+@    {
+
+        LDR     r1,Int_Count                @ Pickup address of interrupt count
+        LDR     r2,[r1, #0]                 @ Pickup interrupt counter
+        SUB     r2,r2,#1                    @ Decrement interrupt counter
+        STR     r2,[r1, #0]                 @ Store interrupt counter
+        CMP     r2,#0
+        BEQ     TCT_Not_Nested_Restore
+
+        @ Restore previous context. 
+
+        LDR     r1,[r13], #4                @ Pickup the saved CPSR
+        
+        MSR     SPSR,r1                     @ Place into saved SPSR
+        LDMIA   r13,{r0-r15}^               @ Return to the point of interrupt
+
+@    }
+@    else
+@    {
+
+TCT_Not_Nested_Restore:
+
+        @ Determine if a thread is active. 
+@        if (TCD_Current_Thread)
+@        {
+
+        LDR     r1,Current_Thread           @ Pickup current thread ptr address
+        LDR     r0,[r1, #0]                 @ Pickup current thread pointer
+        CMP     r0,#0                       @ Determine if a thread is active
+        BEQ     TCT_Idle_Context_Restore    @ If not, idle system restore
+
+        @ Clear the current thread pointer. 
+@            TCD_Current_Thread =  NU_NULL
+
+        MOV     r2,#0                       @ Build NU_NULL value
+        STR     r2,[r1, #0]                 @ Set current thread ptr to NU_NULL
+
+        @ Determine if a time slice is active.  If so, the remaining
+        @ time left on the time slice must be saved in the task's
+        @ control block. 
+@            if (TMD_Time_Slice_State == 0)
+@            {
+
+        LDR     r3,Slice_State              @ Pickup time slice state address
+        LDR     r1,[r3, #0]                 @ Pickup time slice state
+        CMP     r1,#0                       @ Determine if time slice active
+        BNE     TCT_Idle_Context_Restore    @ If not, skip time slice reset
+
+        @ Pickup the remaining portion of the time slice and save it
+        @ in the task's control block. 
+@                REG_Thread_Ptr -> tc_cur_time_slice =  TMD_Time_Slice
+@                TMD_Time_Slice_State =  1
+
+        LDR     r2,Time_Slice               @ Pickup address of time slice left
+        MOV     r1,#1                       @ Build disable time slice value
+        LDR     r2,[r2, #0]                 @ Pickup remaining time slice
+        STR     r1,[r3, #0]                 @ Disable time slice
+        STR     r2,[r0, #TC_CUR_TIME_SLICE] @ Store remaining time slice
+
+@            }
+@        }
+TCT_Idle_Context_Restore:
+
+        @ Reset the system stack pointer. 
+        LDR     r1,System_Stack             @ Pickup address of stack pointer
+        LDR     r2,System_Limit             @ Pickup address of stack limit ptr
+        LDR     r13,[r1, #0]                @ Switch to system stack
+        LDR     r10,[r2, #0]                @ Setup system stack limit
+
+        @ Return to scheduler. 
+
+        B       TCT_Schedule                @ Return to scheduling loop
+
+@    }
+@}
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *      TCT_Activate_HISR                                                
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function activates the specified HISR.  If the HISR is      
+ *      already activated, the HISR's activation count is simply         
+ *      incremented.  Otherwise, the HISR is placed on the appropriate   
+ *      HISR priority list in preparation for execution.                 
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      Application LISRs                                                
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      hisr                                Pointer to HISR to activate  
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      NU_SUCCESS                          Successful completion        
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *                                                                       
+ ************************************************************************
+ */
+
+@STATUS  TCT_Activate_HISR(TC_HCB *hisr)
+@{
+
+	.globl  TCT_Activate_HISR
+TCT_Activate_HISR:
+
+@INT     priority;
+
+
+        @ Lockout interrupts. 
+
+        STR     r4,[r13, #-4]!              @ Save r4
+        MRS     r4,CPSR                     @ Pickup current CPSR
+        ORR     r1,r4,#LOCKOUT              @ Build interrupt lockout value
+        MSR     CPSR,r1                     @ Lockout interrupts
+
+    @ Determine if the HISR is already active. 
+@    if (hisr -> tc_activation_count)
+@    {
+
+        LDR     r1,[r0,#0x40]               @ Pickup current activation count
+        CMP     r1,#0                       @ Is it the first activation?
+        BEQ     TCT_First_Activate          @ Yes, place it on the correct list
+
+    @ Increment the activation count.  Make sure that it does not go
+    @ to zero. 
+@        hisr -> tc_activation_count++;
+
+        ADDS    r1,r1,#1                    @ Increment the activation count
+        STR     r1,[r0,#0x40]               @ Store new activation count
+
+@        if (hisr -> tc_activation_count == 0)
+
+@            hisr -> tc_activation_count =  0xFFFFFFFFUL;
+
+        MVNEQ   r1,#0                       @ If counter rolled-over reset
+        STREQ   r1,[r0,#0x40]               @ Store all ones count
+        B       TCT_Activate_Done           @ Finished with activation
+@    }
+@    else
+@    {
+TCT_First_Activate:
+
+
+        @ Set the activation count to 1. 
+@        hisr -> tc_activation_count =  1;
+
+        MOV     r1,#1                       @ Initial activation count
+        STR     r1,[r0,#0x40]               @ Store initial activation count
+
+        @ Pickup the HISR's priority. 
+@        priority =  hisr -> tc_priority;
+
+        @ Determine if there is something in the given priority list. 
+@        if (TCD_Active_HISR_Tails[priority])
+@        {
+
+        LDRB    r1,[r0,#0x1a]               @ Pickup priority of HISR
+        LDR     r2,HISR_Tails               @ Pickup tail pointer base
+        LDR     r3,[r2,r1,LSL #2]           @ Pickup tail pointer for priority
+        CMP     r3,#0                       @ Is this first HISR at priority?
+        BEQ     TCT_First_HISR              @ No, append to end of HISR list
+
+        @ Something is already on this list.  Add after the tail. 
+@            (TCD_Active_HISR_Tails[priority]) -> tc_active_next =  hisr;
+@            TCD_Active_HISR_Tails[priority] =  hisr;
+
+        STR     r0,[r3,#0x3c]               @ Setup the active next pointer
+        STR     r0,[r2,r1,LSL #2]           @ Setup the tail pointer
+        B       TCT_Activate_Done           @ Finished with activate processing
+@        }
+@        else
+@        {
+TCT_First_HISR:
+
+        @ Nothing is on this list. 
+@           TCD_Active_HISR_Heads[priority] =  hisr;
+@           TCD_Active_HISR_Tails[priority] =  hisr;
+
+        LDR     r3,HISR_Heads               @ Pickup address of head pointers
+        STR     r0,[r2,r1,LSL #2]           @ Set tail pointer to this HISR
+        STR     r0,[r3,r1,LSL #2]           @ Set head pointer to this HISR
+
+        @ Determine the highest priority HISR. 
+@           if (TCD_Active_HISR_Heads[0])
+@               TCD_Execute_HISR =  TCD_Active_HISR_Heads[0];
+@           else if (TCD_Active_HISR_Heads[1])
+@               TCD_Execute_HISR =  TCD_Active_HISR_Heads[1];
+@           else
+@               TCD_Execute_HISR =  TCD_Active_HISR_Heads[2];
+
+        LDR     r1,[r3,#0]                  @ Pickup priority 0 head pointer
+        LDR     r0,Execute_HISR             @ Build address to execute HISR ptr
+        CMP     r1,#0                       @ Is priority 0 active?
+        LDREQ   r1,[r3,#4]                  @ If not, pickup priority 1 head 
+        CMPEQ   r1,#0                       @ Is priority 1 active?
+        LDREQ   r1,[r3,#8]                  @ Else, must be priority 2 active
+        STR     r1,[r0,#0]                  @ Store which ever priority is the
+                                            @   active one
+@       }
+@    }
+TCT_Activate_Done:
+
+        MSR     CPSR,r4                     @ Restore interrupt lockout
+        LDR     r4,[r13], #4                @ Restore corrupted r4
+
+@    return(NU_SUCCESS);
+
+        MOV     r0,#0                       @ Always return NU_SUCCESS
+
+        BX      r14                         @ Return to caller
+
+@}
+
+/*
+ ************************************************************************
+ *                                                                       
+ * FUNCTION                                                              
+ *                                                                       
+ *      TCT_HISR_Shell                                                   
+ *                                                                       
+ * DESCRIPTION                                                           
+ *                                                                       
+ *      This function is the execution shell of each and every HISR.  If 
+ *      the HISR has completed its processing, this shell routine exits  
+ *      back to the system.  Otherwise, it sequentially calls the HISR   
+ *      routine until the activation count goes to zero.                 
+ *                                                                       
+ * CALLED BY                                                             
+ *                                                                       
+ *      HISR Scheduling                                                  
+ *                                                                       
+ * CALLS                                                                 
+ *                                                                       
+ *      hisr -> tc_entry                    Actual entry function of HISR
+ *                                                                       
+ * INPUTS                                                                
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * OUTPUTS                                                               
+ *                                                                       
+ *      None                                                             
+ *                                                                       
+ * HISTORY                                                               
+ *                                                                       
+ *         NAME            DATE                    REMARKS               
+ *                                                                       
+ *      W. Lamie        02-15-1994      Created initial version 1.0      
+ *      D. Lamie        02-15-1994      Verified version 1.0             
+ *                                                                       
+ ************************************************************************
+ */
+
+@VOID    TCT_HISR_Shell(void)
+@{
+        .globl  TCT_HISR_Shell
+TCT_HISR_Shell:
+
+    @ Point at the HISR. 
+@    REG_HISR_Ptr =  (TC_HCB *) TCD_Current_Thread;
+
+        LDR     r0,Current_Thread            @ Build address of thread pointer
+        LDR     r5,[r0, #0]                  @ Pickup control block pointer
+
+@    do
+@    {
+TCT_HISR_Loop:
+
+        @ Call the HISR's entry routine. 
+@        (*(REG_HISR_Ptr -> tc_entry)) ();
+
+/* old TMS470 code:
+
+        .if THUMB = 0
+
+         MOV     r14,r15                     ; Setup return value
+         LDR     r15,[r5,#44h]               ; Call HISR entry function
+        .else
+         LDR     r4,[r5,#44h]                ; Get HISR entry function
+         TST     r4,#1                       ; See if calling Thumb or ARM
+         BNE     Thumbsec
+         MOV     r14,r15                     ; Setup return value
+         BX      r4
+         B       ARMCODE
+Thumbsec:
+         ADD     r14, r15, #1 
+         BX      r4
+         .state16
+ThumbAfterHisr
+         MOV     r1, r15  
+         BX      r1
+        .state32
+        .endif
+*/
+
+	/* new code for the GNU style of ARM/Thumb interworking */
+	ldr	r4, [r5, #TC_HISR_ENTRY]
+	mov	lr, pc
+	bx	r4
+
+        @ Lockout interrupts. 
+
+        MRS     r1,CPSR                     @ Pickup current CPSR
+        ORR     r1,r1,#LOCKOUT              @ Build interrupt lockout 
+        MSR     CPSR,r1                     @ Lockout interrupts
+
+        @ On return, decrement the activation count and check to see if 
+        @ it is 0.  Once it reaches 0, the HISR should be made inactive.
+@        REG_HISR_Ptr -> tc_activation_count--;
+
+
+        LDR     r0,[r5, #0x40]              @ Pickup current activation count
+        SUBS    r0,r0,#1                    @ Subtract and set condition codes
+        STR     r0,[r5, #0x40]              @ Store new activation count
+        BEQ     TCT_HISR_Finished           @ Finished processing HISR
+
+        @ Restore interrupts. 
+
+        LDR     r2,Int_Level                @ Pickup address of interrupt level
+        MRS     r1,CPSR                     @ Pickup current CPSR
+        LDR     r3,[r2, #0]                 @ Pickup interrupt lockout level
+        BIC     r1,r1,#LOCK_MSK             @ Clear lockout bits
+        ORR     r1,r1,r3                    @ Build new interrupt lockout
+        MSR     CPSR,r1                     @ Setup CPSR appropriately
+        B       TCT_HISR_Loop               @ Return to HISR loop
+@    }
+@    while (REG_HISR_Ptr -> tc_activation_count);
+
+TCT_HISR_Finished:
+
+        @ At this point, the HISR needs to be made inactive. 
+
+        @ Determine if this is the only HISR on the given priority list. 
+@    if (REG_HISR_Ptr == TCD_Active_HISR_Tails[REG_HISR_Ptr -> tc_priority])
+@    {
+
+        LDR     r14,HISR_Tails               @ Pickup tail pointers address
+        LDRB    r3,[r5,#0x1a]                @ Pickup priority
+        LDR     r6,[r14,r3,LSL #2]           @ Pickup this priority tail pointer
+        LDR     r2,Execute_HISR              @ Build address to execute HISR ptr
+        MOV     r12,#0                       @ Clear r12
+        LDR     r1,HISR_Heads                @ Pickup head pointers address
+        CMP     r6,r5                        @ Is this priority tail the same as
+                                             @ the current HISR?
+        BNE     TCT_More_HISRs               @ If not, more HISRs at this 
+                                             @ priority
+
+        @ The only HISR on the list.  Clean up the list and check for the
+        @ highest priority HISR. 
+@       TCD_Active_HISR_Heads[REG_HISR_Ptr -> tc_priority] =  NU_NULL;
+@       TCD_Active_HISR_Tails[REG_HISR_Ptr -> tc_priority] =  NU_NULL;
+
+        STR     r12,[r1,r3,LSL #2]            @ Set head pointer to NU_NULL
+        STR     r12,[r14,r3,LSL #2]           @ Set tail pointer to NU_NULL
+
+        @ Determine the highest priority HISR. 
+@       if (TCD_Active_HISR_Heads[0])
+@           TCD_Execute_HISR =  TCD_Active_HISR_Heads[0];
+@       else if (TCD_Active_HISR_Heads[1])
+@           TCD_Execute_HISR =  TCD_Active_HISR_Heads[1];
+@       else
+@           TCD_Execute_HISR =  TCD_Active_HISR_Heads[2];
+
+        LDR     r3,[r1,#0]                    @ Pickup priority 0 head pointer
+        CMP     r3,#0                         @ Is there an HISR active?
+        LDREQ   r3,[r1,#4]                    @ If not, pickup priority 1 pointer
+        CMPEQ   r3,#0                         @ Is there an HISR active?
+        LDREQ   r3,[r1,#8]                    @ If not, pickup priority 2 pointer
+        STR     r3,[r2,#0]                    @ Setup execute HISR pointer
+        B       TCT_HISR_Exit                 @ Exit HISR processing
+@    }
+@    else
+@    {
+
+TCT_More_HISRs:
+
+        @ Move the head pointer to the next HISR in the list. 
+@        TCD_Active_HISR_Heads[REG_HISR_Ptr -> tc_priority] =  
+@                                        REG_HISR_Ptr -> tc_active_next;
+
+        @ Also set the TCD_Execute_HISR pointer. 
+@        TCD_Execute_HISR =  REG_HISR_Ptr -> tc_active_next;
+
+        LDR     r14,[r5,#0x3c]                @ Pickup next HISR to activate
+        STR     r14,[r1,r3,LSL #2]            @ Setup new head pointer
+        STR     r14,[r2, #0]                  @ Setup execute HISR pointer
+@    }
+
+TCT_HISR_Exit:
+
+        @ Build fake return to the top of this loop.  The next time the HISR
+        @ is activated, it will return to the top of this function. 
+
+        LDR     r14,HISR_Shell                @ Pickup address of shell entry
+        STMDB   r13!,{r4-r12,r14}             @ Save minimal context of thread on
+                                              @ the current stack
+        MOV     r2,#0                         @ Build solicited stack type value
+                                              @ and NU_NULL value
+#if 1	/* was .if THUMB */
+        STR     r2,[r13, #-4]!                @ Save state mask
+#endif
+        STR     r2,[r13, #-4]!                @ Place it on the top of the stack
+
+        @ Clear the current thread control block. 
+@    TCD_Current_Thread =  NU_NULL;
+
+        LDR     r1,Current_Thread            @ Pickup current thread ptr address
+        STR     r2,[r1, #0]                  @ Set current thread pointer to 
+                                             @   NU_NULL
+
+        @ Save off the current stack pointer in the control block. 
+@    REG_HISR_Ptr -> tc_stack_pointer =  (VOID *) REG_Stack_Ptr;
+
+         
+        STR     r13,[r5, #0x2c]              @ Save the thread's stack pointer
+
+
+        @ Switch to the system stack. 
+@    REG_Stack_Ptr =  (BYTE_PTR) TCD_System_Stack;
+
+        LDR     r1,System_Stack              @ Pickup address of stack pointer
+        LDR     r2,System_Limit              @ Pickup address of stack limit ptr
+        LDR     r13,[r1, #0]                 @ Switch to system stack
+        LDR     r10,[r2, #0]                 @ Setup system stack limit
+
+        @ Transfer control to the main scheduling loop. 
+
+        B       TCT_Schedule                 @ Return to main scheduling loop
+@}
+
+/* FreeCalypso addition, used by riviera/rvf/rvf_task.c: */
+	.globl	INT_Check_IRQ_Mask
+INT_Check_IRQ_Mask:
+	MRS	r0,CPSR
+	BX	lr
+