SWCU194 March 2023 CC1314R10 , CC1354P10 , CC1354R10 , CC2674P10 , CC2674R10
To enter the ROM bootloader even when a valid image is in Flash, a bootloader backdoor is implemented. The CCFG parameter BL_ENABLE can enable this backdoor. The backdoor functionality uses a configurable I/O pin (CCFG parameter BL_PIN_NUMBER) and a configurable I/O pin level (CCFG parameter BL_LEVEL).
If backdoor functionality is enabled, externally applying the configurable signal level on the configurable I/O pin can force ROM bootloader entry upon reset. If the backdoor is enabled and a valid Flash image is present, start-up code checks the level of the I/O pin. If the configured I/O pin level matches the configured signal level, the ROM bootloader does not transfer control to the Flash image.
If the backdoor pin configuration matches one of the UART0 or SPI0 pins, the external user must de-assert the backdoor signal before transmitting on the UART0 or SPI0 interface.
In TI distributed software, the CCFG parameters called BL_ENABLE, BL_PIN_NUMBER and BL_LEVEL are configured by the values of the following defines of the CCFG region.
SET_CCFG_BL_CONFIG_BL_ENABLE
SET_CCFG_BL_CONFIG_BL_PIN_NUMBER
SET_CCFG_BL_CONFIG_BL_LEVEL
When using the bootloader backdoor functionality, the pin configured as backdoor (BL_PIN_NUMBER) will be configured to enable a pull level opposite to the configured I/O pin level while checking the backdoor level.