It First !link! - Flashing Lock Flag Is Locked. Please Unlock
> flash write_image erase firmware.bin 0x08000000 Error: STM32 flash write protection error Error: dap service can't execute requested operation Error: Flash lock flag is locked. Please unlock it first. At this point, the flash controller rejects the write command. The following steps are ordered from safest to most aggressive. Always backup existing firmware and data before proceeding. 5.1 Software Unlock via Debugger For most ARM Cortex-M devices, the unlock is performed by clearing the Option Bytes register.
// Pseudo-code for bootloader if (flash_is_locked(FLASH_SECTOR_BOOT)) flash_unlock(); flash_clear_flag(FLASH_FLAG_WRPERR); flashing lock flag is locked. please unlock it first
| Device Family | Unlock Command | |---------------|----------------| | STM32 (with ST-Link) | STM32_Programmer_CLI -c port=swd -ob rdp=0xAA | | ESP32 | esptool.py --port COM3 write_flash_status --non-volatile 0 | | NXP LPC | lpcscrypt unlock –device LPC55S69 | | Generic J-Link | JLinkExe -device CORTEX-M4 -if SWD -speed 4000 -autoconnect 1 -CommanderScript unlock.jlink | > flash write_image erase firmware
Document ID: ERR-FLASH-2024-01 Type: Troubleshooting & Root Cause Analysis Target Audience: Firmware engineers, embedded systems developers, technical support 1. Abstract The error message “Flashing lock flag is locked. Please unlock it first” typically appears during firmware updates, bootloader operations, or in-system programming (ISP) of microcontrollers (e.g., STM32, ESP32, or custom SoCs). This paper examines the root cause, the underlying memory protection mechanism, and step-by-step methods to safely resolve the issue without corrupting the flash memory. 2. Background Modern embedded systems implement flash lock flags (also called option bytes , security bits , or write protection registers ) to prevent accidental overwriting of critical code regions (e.g., bootloader, calibration data). When the lock flag is set, any attempt to erase or reprogram the corresponding flash sector triggers the error message. The following steps are ordered from safest to
openocd -f interface/stlink.cfg -f target/stm32f4x.cfg -c "init; stm32f4x unlock 0; reset; exit"
The lock mechanism can exist at multiple levels:
STM32_Programmer_CLI -c port=swd -ob displ STM32_Programmer_CLI -c port=swd -ob nSWBOOT0=1 STM32_Programmer_CLI -c port=swd -ob WRP_SECTOR=0x00000000 Some devices clear lock flags automatically after a full chip erase:
