SWCU193 April 2023 CC2340R2 , CC2340R5 , CC2340R5-Q1
The application may communicate with the bootloader through the so-called REG3V3 register the contents of which survives reset and any power mode transition (including prolonged shutdown and reset power state). The typical use case is a bootloader that performs a FW image update (from image in internal or external SPI flash) when instructed by application. The bootloader may also use REG3V3 to keep track of state/progress of the firmware update process across multiple resets.
The REG3V3 registers::
A bootloader must remember to clear flags/fields passed from the application as the request has been dealt with so that it doesn't occur multiple times.