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-rw-r--r--scripts/stubs/stm32_opterase.S53
1 files changed, 53 insertions, 0 deletions
diff --git a/scripts/stubs/stm32_opterase.S b/scripts/stubs/stm32_opterase.S
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+++ b/scripts/stubs/stm32_opterase.S
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+@; Assembler sequence to erase option bytes on STM32
+@; Takes no parameters, ends with BKPT instruction
+.global _start
+
+.equ FLASHBASE, 0x40022000
+
+.equ KEY1, 0x45670123
+.equ KEY2, 0xCDEF89AB
+
+.equ FLASH_KEY, 0x04
+.equ FLASH_OPTKEY, 0x08
+.equ FLASH_CR, 0x10
+.equ FLASH_SR, 0x0C
+
+.equ OPTER, 0x20
+.equ STRT, 0x40
+
+.equ BSY, 0x01
+
+.syntax unified
+
+_start:
+ @; Load FLASH controller base address
+ ldr r0, =FLASHBASE
+
+ @; Do unlocking sequence
+ ldr r1, =KEY1
+ str r1, [r0, #FLASH_KEY]
+ ldr r1, =KEY2
+ str r1, [r0, #FLASH_KEY]
+
+ @; Same for option bytes
+ ldr r1, =KEY1
+ str r1, [r0, #FLASH_OPTKEY]
+ ldr r1, =KEY2
+ str r1, [r0, #FLASH_OPTKEY]
+
+ @; Set OPTER bit in FLASH_CR
+ ldr r1, [r0, #FLASH_CR]
+ orr r1, r1, #OPTER
+ str r1, [r0, #FLASH_CR]
+ @; Set STRT bit in FLASH_CR
+ orr r1, r1, #STRT
+ str r1, [r0, #FLASH_CR]
+
+_wait: @; Wait for BSY bit to clear
+ ldr r4, [r0, #FLASH_SR]
+ mov r6, #BSY
+ tst r4, r6
+ bne _wait
+
+ bkpt
+