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annotate Flash-boot-modes @ 33:7aed57fc1928

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FC-modem-family article fully rewritten for the new reality of FC Tango modules
author Mychaela Falconia <falcon@freecalypso.org>
date Mon, 28 Sep 2020 00:48:17 +0000
parents dc0e9c91d54a
children
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dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
1 The Calypso chip includes an on-die boot ROM that allows the boot process to be
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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2 interrupted and diverted by an external host sending some special characters
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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3 into either of the two UARTs; this mechanism is what allows us to load code into
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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4 RAM and to reload the flash on Calypso GSM devices without having to resort to
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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5 JTAG or chip desoldering or other extreme measures. In normal operation, when
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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6 the boot path is NOT being diverted by an external serial download, the boot ROM
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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7 transfers control to the regular firmware in the flash - but there are two
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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8 different modes in which the flash fw image may be booted.
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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9
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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10 In order for the flash fw image to be considered bootable by the Calypso boot
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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11 ROM, the 32-bit word at flash address 0x2000 must equal either 0 or 1; if it
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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12 equals any other value, the boot ROM will consider the flash fw image to be
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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13 invalid (e.g., blank flash) and will wait forever for a serial download instead
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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14 of proceeding with flash boot. Depending on whether this word at 0x2000 equals
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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15 0 or 1, the flash fw image will be booted in one of two very different ways;
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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16 we shall call them flash boot mode 0 and flash boot mode 1, respectively.
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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17
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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18 In flash boot mode 0 the following 32-bit word at flash address 0x2004 must
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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19 contain the address of the flash fw image entry point (ARM/Thumb selection in
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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20 the least-significant bit); the boot ROM will simply jump to this address with
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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21 a BX instruction. When the flash fw image is booted in this manner, the boot
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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22 ROM is still mapped at address 0 and the first 8 KiB of flash are inaccessible
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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23 except via the 0x03000000 alternate mapping, unless the firmware later changes
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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24 the FFFF:FB10 register. This boot mode is intended for flash fw images that
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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25 use the interrupt and exception vectors in the ROM (branching to IRAM addresses
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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26 0x80001C-0x800034) for their interrupt and exception handling.
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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27
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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28 Flash boot mode 1 is different: instead of jumping directly to the flash fw
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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29 image, the boot ROM copies a small piece of its code into IRAM and jumps to that
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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30 code; the copied code disables the boot ROM via the FFFF:FB10 register (puts
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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31 the external flash at address 0) and induces a processor reset through the
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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32 watchdog timer. It is not clear to us exactly what blocks are affected by the
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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33 watchdog reset, but bits 9:8 of the FFFF:FB10 register are not reset, hence
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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34 the ARM processor now boots from the reset vector in the flash as if the boot
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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35 ROM weren't there - and the latter really is not there after having disabled
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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36 itself.
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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37
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
38 Flash boot mode 0 is only usable on Calypso C035 silicon (the "new" kind);
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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39 while all commercial Calypso GSM devices targeted by FreeCalypso feature Calypso
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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40 chips of the correct "new" kind, the people at TI who wrote and maintained their
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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41 official firmware also had to work with older Calypso C05 chips featured on the
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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42 early D-Sample and Leonardo boards. The earlier boot ROM code version in those
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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43 early Calypso chips also implements the two boot modes which we call mode 0 and
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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44 mode 1, but its implementation of mode 0 is broken and unusable, therefore TI's
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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45 firmware people only used flash boot mode 1. On the other hand, newer firmware
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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46 designs made for current rather than historical hardware will probably find
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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47 mode 0 to be cleaner, more intuitive and more convenient.
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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48
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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49 All TI official firmwares use flash boot mode 1, our FreeCalypso Magnetite
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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50 firmware does likewise, being a direct derivative of TI's TCS211 fw, but our
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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51 gcc-built FC Selenite firmware uses flash boot mode 0, as the assembly code
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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52 pieces and linker script magic are entirely new (our own original design) in
dc0e9c91d54a Flash-boot-modes article added (migrated from freecalypso-tools)
Mychaela Falconia <falcon@freecalypso.org>
parents:
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53 the gcc-built version.