diff src/nucleus/tms470/tmt.s @ 40:614668bbbc4f

Nucleus: tmt.s ported over from FreeNucleus by XVilka
author Mychaela Falconia <falcon@freecalypso.org>
date Tue, 17 Jul 2018 07:55:01 +0000
parents
children
line wrap: on
line diff
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/nucleus/tms470/tmt.s	Tue Jul 17 07:55:01 2018 +0000
@@ -0,0 +1,725 @@
+;************************************************************************
+;*                                                                       
+;*               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                        
+;*                                                                       
+;*      tmt.s                   Nucleus PLUS\ARM925\Code Composer 1.14.1 
+;*                                                                       
+;* COMPONENT                                                             
+;*                                                                       
+;*      TM - Timer Management                                            
+;*                                                                       
+;* DESCRIPTION                                                           
+;*                                                                       
+;*      This file contains the target dependent routines of the timer    
+;*      management component.                                            
+;*                                                                       
+;* FUNCTIONS                                                             
+;*                                                                       
+;*      TMT_Set_Clock                       Set system clock             
+;*      TMT_Retrieve_Clock                  Retrieve system clock        
+;*      TMT_Read_Timer                      Read count-down timer        
+;*      TMT_Enable_Timer                    Enable count-down timer      
+;*      TMT_Adjust_Timer                    Adjust count-down timer      
+;*      TMT_Disable_Timer                   Disable count-down timer     
+;*      TMT_Retrieve_TS_Task                Retrieve time-sliced task ptr
+;*      TMT_Timer_Interrupt                 Process timer interrupt      
+;*                                                                       
+;* DEPENDENCIES                                                          
+;*                                                                       
+;*      tc_extr.h                           Thread Control functions     
+;*      tm_extr.h                           Timer 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.
+LOCKOUT                     .equ    00C0h   ; Interrupt lockout value
+
+	.state32
+
+;**********************************
+;* EXTERNAL VARIABLE DECLARATIONS *
+;**********************************
+; Define external inner-component global data references.
+;extern VOID           *TCD_Current_Thread;
+;extern UNSIGNED        TMD_System_Clock;
+;extern UNSIGNED        TMD_Timer;
+;extern INT             TMD_Timer_State;
+;extern UNSIGNED        TMD_Time_Slice;
+;extern TC_TCB         *TMD_Time_Slice_Task;
+;extern INT             TMD_Time_Slice_State;
+;extern TC_HCB          TMD_HISR;
+
+        .ref  _TCD_Current_Thread
+        .ref  _TMD_System_Clock
+        .ref  _TMD_Timer
+        .ref  _TMD_Timer_State
+        .ref  _TMD_Time_Slice
+        .ref  _TMD_Time_Slice_Task
+        .ref  _TMD_Time_Slice_State
+        .ref  _TMD_HISR
+        .ref  _TCD_Interrupt_Level
+
+; Define activate HISR function.
+;STATUS  TCT_Activate_HISR(TC_HCB *hisr);
+
+        .ref  _TCT_Activate_HISR
+
+    .text
+;**********************************
+;* LOCAL VARIABLE DECLARATIONS    *
+;**********************************
+; Define various data structure pointers so their addresses 
+; can be obtained in a PC-relative manner.
+
+System_Clock
+        .word     _TMD_System_Clock
+
+Timer
+        .word     _TMD_Timer
+
+Timer_State
+        .word     _TMD_Timer_State
+
+Slice_State
+        .word     _TMD_Time_Slice_State
+
+Time_Slice
+        .word     _TMD_Time_Slice
+
+Current_Thread
+        .word     _TCD_Current_Thread
+
+Slice_Task
+        .word     _TMD_Time_Slice_Task
+
+HISR
+        .word     _TMD_HISR
+
+Int_Level
+        .word     _TCD_Interrupt_Level
+
+;************************************************************************
+;*                                                                       
+;* FUNCTION                                                              
+;*                                                                       
+;*      TMT_Set_Clock                                                    
+;*                                                                       
+;* DESCRIPTION                                                           
+;*                                                                       
+;*      This function sets the system clock to the specified value.      
+;*                                                                       
+;* CALLED BY                                                             
+;*                                                                       
+;*      Application                                                      
+;*                                                                       
+;* CALLS                                                                 
+;*                                                                       
+;*      None                                                             
+;*                                                                       
+;* INPUTS                                                                
+;*                                                                       
+;*      new_value                           New value for the clock      
+;*                                                                       
+;* 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  TMT_Set_Clock(UNSIGNED new_value)
+;{
+    .def    $TMT_Set_Clock
+$TMT_Set_Clock                              ; Dual-state interworking veneer
+    .state16
+    BX  r15
+    NOP
+    .state32
+    B   _TMT_Set_Clock
+
+        .def    _TMT_Set_Clock
+_TMT_Set_Clock
+
+; Set the system clock to the specified value.
+;    TMD_System_Clock =  new_value;
+
+        LDR     r1,System_Clock             ; Build address of system clock
+        STR     r0,[r1,#0]                  ; Store new system clock value
+
+        BX      r14                         ; Return to caller
+
+;}
+
+;************************************************************************
+;*                                                                       
+;* FUNCTION                                                              
+;*                                                                       
+;*      TMT_Retrieve_Clock                                               
+;*                                                                       
+;* DESCRIPTION                                                           
+;*                                                                       
+;*      This function returns the current value of the system clock.     
+;*                                                                       
+;* CALLED BY                                                             
+;*                                                                       
+;*      Application                                                      
+;*                                                                       
+;* CALLS                                                                 
+;*                                                                       
+;*      None                                                             
+;*                                                                       
+;* INPUTS                                                                
+;*                                                                       
+;*      None                                                             
+;*                                                                       
+;* OUTPUTS                                                               
+;*                                                                       
+;*      TMD_System_Clock                    Value of system clock        
+;*                                                                       
+;* HISTORY                                                               
+;*                                                                       
+;*         NAME            DATE                    REMARKS               
+;*                                                                       
+;*      W. Lamie        02-15-1994      Created initial version 1.0      
+;*      D. Lamie        02-15-1994      Verified version 1.0             
+;*                                                                       
+;************************************************************************
+;UNSIGNED  TMT_Retrieve_Clock(void)
+;{
+    .def    $TMT_Retrieve_Clock
+$TMT_Retrieve_Clock                         ; Dual-state interworking veneer   
+    .state16
+    BX  r15
+    NOP
+    .state32
+    B   _TMT_Retrieve_Clock
+
+        .def    _TMT_Retrieve_Clock
+_TMT_Retrieve_Clock
+
+; Return the current value of the system clock.
+;    return(TMD_System_Clock);
+
+        LDR     r0,System_Clock             ; Build address to system clock
+        LDR     r0,[r0,#0]                  ; Pickup system clock contents
+
+        BX      r14                         ; Return to caller
+
+;}
+
+;************************************************************************
+;*                                                                       
+;* FUNCTION                                                              
+;*                                                                       
+;*      TMT_Read_Timer                                                   
+;*                                                                       
+;* DESCRIPTION                                                           
+;*                                                                       
+;*      This function returns the current value of the count-down timer. 
+;*                                                                       
+;* CALLED BY                                                             
+;*                                                                       
+;*      TMC_Start_Timer                     Start timer function         
+;*                                                                       
+;* CALLS                                                                 
+;*                                                                       
+;*      None                                                             
+;*                                                                       
+;* INPUTS                                                                
+;*                                                                       
+;*      None                                                             
+;*                                                                       
+;* OUTPUTS                                                               
+;*                                                                       
+;*      TMD_Timer                           Value of count-down timer    
+;*                                                                       
+;* HISTORY                                                               
+;*                                                                       
+;*         NAME            DATE                    REMARKS               
+;*                                                                       
+;*      W. Lamie        02-15-1994      Created initial version 1.0      
+;*      D. Lamie        02-15-1994      Verified version 1.0             
+;*                                                                       
+;************************************************************************
+;UNSIGNED  TMT_Read_Timer(void)
+;{
+    .def    $TMT_Read_Timer
+$TMT_Read_Timer                             ; Dual-state interworking veneer
+    .state16
+    BX  r15
+    NOP
+    .state32
+    B   _TMT_Read_Timer
+
+        .def    _TMT_Read_Timer
+_TMT_Read_Timer
+
+; Return the current value of the count-down timer.
+;    return(TMD_Timer);
+
+        LDR     r0,Timer                    ; Build address to timer
+        LDR     r0,[r0,#0]                  ; Pickup timer contents
+
+        BX      r14                         ; Return to caller
+
+;}
+
+;************************************************************************
+;*                                                                       
+;* FUNCTION                                                              
+;*                                                                       
+;*      TMT_Enable_Timer                                                 
+;*                                                                       
+;* DESCRIPTION                                                           
+;*                                                                       
+;*      This function enables the count-down timer with the specified    
+;*      value.                                                           
+;*                                                                       
+;* CALLED BY                                                             
+;*                                                                       
+;*      TMC_Start_Timer                     Start timer function         
+;*      TMC_Timer_Task                      Timer expiration task        
+;*                                                                       
+;* CALLS                                                                 
+;*                                                                       
+;*      None                                                             
+;*                                                                       
+;* INPUTS                                                                
+;*                                                                       
+;*      time                                New count-down time          
+;*                                                                       
+;* 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  TMT_Enable_Timer(UNSIGNED time)
+;{
+    .def    $TMT_Enable_Timer
+$TMT_Enable_Timer                           ; Dual-state interworking veneer
+    .state16
+    BX  r15
+    NOP
+    .state32
+    B   _TMT_Enable_Timer
+
+        .def    _TMT_Enable_Timer
+_TMT_Enable_Timer
+
+; Place the new time value into the count-down timer.
+;    TMD_Timer =  time;
+
+        LDR     r1,Timer                    ; Build address of timer
+        STR     r0,[r1,#0]                  ; Store new timer value
+
+; Indicate that the timer is active.
+;    TMD_Timer_State =  TM_ACTIVE;
+
+        MOV     r0,#0                       ; Build TM_ACTIVE value
+        LDR     r1,Timer_State              ; Build address of timer state var
+        STR     r0,[r1,#0]                  ; Change the state to active
+
+        BX      r14                         ; Return to caller
+
+;}
+
+;************************************************************************
+;*                                                                       
+;* FUNCTION                                                              
+;*                                                                       
+;*      TMT_Adjust_Timer                                                 
+;*                                                                       
+;* DESCRIPTION                                                           
+;*                                                                       
+;*      This function adjusts the count-down timer with the specified    
+;*      value, if the new value is less than the current.                
+;*                                                                       
+;* CALLED BY                                                             
+;*                                                                       
+;*      None                                                             
+;*                                                                       
+;* CALLS                                                                 
+;*                                                                       
+;*      None                                                             
+;*                                                                       
+;* INPUTS                                                                
+;*                                                                       
+;*      time                                New count-down time.         
+;*                                                                       
+;* 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             
+;*      C. Meredith     08-27-1994      Corrected bug in new timer       
+;*                                        adjust routine, resulting in   
+;*                                        version 1.1a                   
+;*      W. Lamie        08-27-1994      Verified version 1.1a            
+;*                                                                       
+;************************************************************************
+;VOID  TMT_Adjust_Timer(UNSIGNED time)
+;{
+    .def    $TMT_Adjust_Timer
+$TMT_Adjust_Timer                           ; Dual-state interworking veneer
+    .state16
+    BX  r15
+    NOP
+    .state32
+    B   _TMT_Adjust_Timer
+
+        .def    _TMT_Adjust_Timer
+_TMT_Adjust_Timer
+
+; Lockout all interrupts
+;    TMD_Timer_State =  TM_NOT_ACTIVE;
+
+        MRS     r3,CPSR                     ; Pickup current CPSR
+        ORR     r2,r3,#LOCKOUT              ; Build lockout CPSR
+        MSR     CPSR,r2                     ; Setup new CPSR interrupt bits
+
+; Check for the new value is less than the current time value
+;    if (time < TMD_Timer)
+
+        LDR     r1,Timer                    ; Build address to timer var
+        LDR     r2,[r1,#0]                  ; read value of the timer
+        CMP     r2,r0                       ; Do Timer - time > 0, means
+        BLT     TMT_No_Adjust               ; time < Timer.
+
+;        Adjust the time 
+;        TMD_Timer = time;
+
+        STR     r0,[r1,#0]                  ; load passed in timer value
+
+; Return to caller after restoring interrupts
+
+TMT_No_Adjust:
+
+        MSR     CPSR,r3                     ; Setup new CPSR enable bits
+
+        BX      r14                         ; Return to caller
+;}
+
+;************************************************************************
+;*                                                                       
+;* FUNCTION                                                              
+;*                                                                       
+;*      TMT_Disable_Timer                                                
+;*                                                                       
+;* DESCRIPTION                                                           
+;*                                                                       
+;*      This function disables the count-down timer.                     
+;*                                                                       
+;* CALLED BY                                                             
+;*                                                                       
+;*      TMC_Start_Timer                     Start timer function         
+;*      TMC_Timer_Task                      Timer expiration task        
+;*                                                                       
+;* 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  TMT_Disable_Timer(void)
+;{
+    .def    $TMT_Disable_Timer
+$TMT_Disable_Timer                          ; Dual-state interworking veneer
+    .state16
+    BX  r15
+    NOP
+    .state32
+    B   _TMT_Disable_Timer
+
+        .def    _TMT_Disable_Timer
+_TMT_Disable_Timer
+
+; Disable the count-down timer.
+;    TMD_Timer_State =  TM_NOT_ACTIVE;
+
+        MOV     r1,#1                       ; Build TM_NOT_ACTIVE value
+        LDR     r0,Timer_State              ; Build address to timer state var
+        STR     r1,[r0,#0]                  ; Change timer state to not active
+
+        BX      r14                         ; Return to caller
+;}
+
+;************************************************************************
+;*                                                                       
+;* FUNCTION                                                              
+;*                                                                       
+;*      TMT_Retreive_TS_Timer                                            
+;*                                                                       
+;* DESCRIPTION                                                           
+;*                                                                       
+;*      This function returns the time-sliced task pointer.              
+;*                                                                       
+;* CALLED BY                                                             
+;*                                                                       
+;*      TMC_Timer_HISR                      Timer HISR                   
+;*                                                                       
+;* CALLS                                                                 
+;*                                                                       
+;*      None                                                             
+;*                                                                       
+;* INPUTS                                                                
+;*                                                                       
+;*      None                                                             
+;*                                                                       
+;* OUTPUTS                                                               
+;*                                                                       
+;*      TMD_Time_Slice_Task                 Time sliced task pointer     
+;*                                                                       
+;* HISTORY                                                               
+;*                                                                       
+;*         NAME            DATE                    REMARKS               
+;*                                                                       
+;*      C. Meredith     03-01-1994      Created initial version 1.1      
+;*      D. Lamie        03-18-1994      Verified version 1.1             
+;*                                                                       
+;************************************************************************
+;NU_TASK TMT_Retrieve_TS_Task (VOID)
+;{
+    .def    $TMT_Retrieve_TS_Task
+$TMT_Retrieve_TS_Task                        ; Dual-state interworking veneer
+    .state16
+    BX  r15
+    NOP
+    .state32
+    B   _TMT_Retrieve_TS_Task
+
+        .def    _TMT_Retrieve_TS_Task
+_TMT_Retrieve_TS_Task
+
+; Read the current TMD_Time_Slice_Task variable and load for
+; return to caller.
+
+        LDR     r1,Slice_Task                ; Build address to timer slice var
+        LDR     r0,[r1,#0]                   ; Get task pointer to be returned
+
+; Return to caller time slice value back to caller
+
+        BX      r14                          ; Return to caller
+
+;}
+
+;************************************************************************
+;*                                                                       
+;* FUNCTION                                                              
+;*                                                                       
+;*      TMT_Timer_Interrupt                                              
+;*                                                                       
+;* DESCRIPTION                                                           
+;*                                                                       
+;*      This function processes the actual hardware interrupt.           
+;*      Processing includes updating the system clock and the count-     
+;*      down timer and the time-slice timer.  If one or both of the      
+;*      timers expire, the timer HISR is activated.                      
+;*                                                                       
+;* CALLED BY                                                             
+;*                                                                       
+;*      Interrupt Vector                                                 
+;*                                                                       
+;* CALLS                                                                 
+;*                                                                       
+;*      TCT_Activate_HISR                   Activate timer HISR          
+;*      TCT_Interrupt_Context_Save          Save interrupted context     
+;*      TCT_Interrupt_Context_Restore       Restore interrupted context  
+;*                                                                       
+;* 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  TMT_Timer_Interrupt(void)
+;{
+        .def  _TMT_Timer_Interrupt
+_TMT_Timer_Interrupt
+
+        MRS     r1,CPSR                         ; Pickup current CPSR
+        ORR     r1,r1,#LOCKOUT                  ; Set the interrupt lockout bits
+        MSR     CPSR,r1                         ; Lockout interrupts
+
+; Increment the system clock.
+;    TMD_System_Clock++;
+
+        LDR     r0,System_Clock                 ; Pickup system clock address
+        LDR     r1,[r0,#0]                      ; Pickup system clock contents
+        ADD     r1,r1,#1                        ; Increment system clock
+        STR     r1,[r0,#0]                      ; Store new system clock value
+
+; Determine if the count-down timer is active.
+;    if (TMD_Timer_State == TM_ACTIVE)
+;    {
+
+        LDR     r1,Timer_State                  ; Build address to timer state flag
+        LDR     r0,[r1,#0]                      ; Pickup timer state
+        MOV     r3,#2                           ; Build expired value
+        CMP     r0,#0                           ; Is there a timer active?
+        BNE     TMT_No_Timer_Active             ; No, skip timer processing
+
+; Decrement the count-down timer.
+;        TMD_Timer--;
+
+        LDR     r0,Timer                        ; Build timer address
+        LDR     r2,[r0,#0]                      ; Pickup the current timer value
+
+; Test if the Timer is at 0 and if so skip the decrement 
+        cmp     r2,#1
+        beq     EXPIRED
+
+        SUBS    r2,r2,#1                        ; Decrement the timer value
+        STR     r2,[r0,#0]                      ; Store the new timer value
+
+        bne     TMT_No_Timer_Active             ; Skip over the Set Timer State
+
+; Determine if the timer has expired. If so, modify the state 
+; to indicate that it has expired.
+;        if (TMD_Timer == 0)
+
+;            TMD_Timer_State =  TM_EXPIRED;
+
+EXPIRED:
+        STREQ   r3,[r1,#0]                      ; Change the timer state to 
+                                                ; expired
+
+;    }
+TMT_No_Timer_Active:
+
+; Determine if the time-slice timer is active.  Note that the parameters
+; for the time-slice are controlled by the Thread Control (TC) 
+; component.
+;    if (TMD_Time_Slice_State == TM_ACTIVE)
+;    {
+        LDR     r0,Slice_State                  ; Build time slice state address
+        LDR     r2,[r0,#0]                      ; Pickup time slice state
+        CMP     r2,#0                           ; Is there a time slice active?
+        BNE     TMT_No_Time_Slice_Active        ; No, skip time slice processing
+
+; Decrement the time slice counter.
+;        TMD_Time_Slice--;
+
+        LDR     r2,Time_Slice                   ; Build time slice address
+        LDR     r3,[r2,#0]                      ; Pickup the time slice value
+        SUBS    r3,r3,#1                        ; Decrement the time slice
+        STR     r3,[r2,#0]                      ; Store the new time slice value
+
+        ; Determine if the time-slice timer has expired. If so, modify the
+        ; time-slice state to indicate that it has.
+;        if (TMD_Time_Slice == 0)
+;        {
+
+        BNE     TMT_No_Time_Slice_Active        ; Has time slice expired?
+
+;            TMD_Time_Slice_State =  TM_EXPIRED;
+
+        MOV     r3,#2                           ; Build TM_EXPIRED value
+        STR     r3,[r0,#0]                      ; Indicate time slice is expired
+
+        ; Copy the current thread into the time-slice task pointer.
+;            TMD_Time_Slice_Task =  TCD_Current_Thread;
+
+        LDR     r2,Current_Thread               ; Pickup current thread pointer adr
+        LDR     r2,[r2,#0]                      ; Pickup current thread pointer
+        LDR     r3,Slice_Task                   ; Pickup time slice task pointer ad
+        STR     r2,[r3,#0]                      ; Store current thread pointer
+
+;            ((TC_TCB *) TCD_Current_Thread) -> tc_cur_time_slice =  1;
+
+        MOV     r3,#1                           ; For safety, place a minimal time-
+        STR     a4,[a3,#20h]!                   ; slice into the task's control
+                                                ; block
+
+;        }
+;    }
+TMT_No_Time_Slice_Active:
+
+    ; Determine if either of the basic timers have expired.  If so, 
+    ; activate the timer HISR.
+;    if ((TMD_Timer_State == TM_EXPIRED) ||
+;        (TMD_Time_Slice_State == TM_EXPIRED))
+;    {
+
+        LDR     r1,[r1,#0]                      ; Pickup timer state 
+        CMP     r1,#2                           ; Does it indicate expiration?
+        LDRNE   r0,[r0,#0]                      ; Pickup time slice state
+        CMPNE   r0,#2                           ; Does it indicate expiration?
+         
+        BXNE    r14                             ; Return if no expiration
+
+        ; Activate the HISR timer function.
+;        TCT_Activate_HISR(&TMD_HISR);
+
+        STR     r14,[r13, #-4]!                 ; Save r14 on the stack
+        LDR     r0,HISR                         ; Build address of timer HISR
+        BL      _TCT_Activate_HISR              ; Activate timer HISR
+        LDR     r14,[r13], #4                   ; Recover return address
+;    }
+
+        BX      r14                             ; Return to caller
+
+;}
+        .end
+
+