53 lines
898 B
ArmAsm
53 lines
898 B
ArmAsm
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@; Assembler sequence to program option bytes on STM32
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@; Takes option address in r0 and value in r1.
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@; Ends with BKPT instruction
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.global _start
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.equ FLASHBASE, 0x40022000
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.equ KEY1, 0x45670123
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.equ KEY2, 0xCDEF89AB
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.equ FLASH_KEY, 0x04
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.equ FLASH_OPTKEY, 0x08
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.equ FLASH_CR, 0x10
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.equ FLASH_SR, 0x0C
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.equ OPTPG, 0x10
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.equ BSY, 0x01
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.syntax unified
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_start:
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@; Load FLASH controller base address
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ldr r2, =FLASHBASE
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@; Do unlocking sequence
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ldr r3, =KEY1
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str r3, [r2, #FLASH_KEY]
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ldr r3, =KEY2
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str r3, [r2, #FLASH_KEY]
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@; Same for option bytes
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ldr r3, =KEY1
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str r3, [r2, #FLASH_OPTKEY]
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ldr r3, =KEY2
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str r3, [r2, #FLASH_OPTKEY]
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@; Set OPTPG bit in FLASH_CR
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ldr r3, [r2, #FLASH_CR]
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orr r3, r3, #OPTPG
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str r3, [r2, #FLASH_CR]
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@; Write data at address
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strh r1, [r0]
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_wait: @; Wait for BSY bit to clear
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ldr r4, [r2, #FLASH_SR]
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mov r6, #BSY
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tst r4, r6
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bne _wait
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bkpt
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