Address	Notes	Size
0x0	Bootloader start	code up to 0x2FFE bytes
0x2FFE	Bootloader CRC	half-word
0x3000	App image A start	code up to 0xE7F4 (~59K) bytes
0x117F8	App image A CRC check length	word
0x117FC	App image A CRC check value	word
0x117FC	App image B start	code up to 0xE7F4 (~59K) bytes
0x1FFF0	App image B CRC check length	word
0x1FFF4	App image B CRC check value	word
0x1FFF8	Reserved section, contains boot select parameter	8 bytes
0x20000	End of NVM	end

Additional Information

This bootloader was specifically written for the REB1 board, so it assumes a M95M01 ST EEPROM is used to load the application code. The bootloader will also delay for a configurable amount of time before booting. This allows to catch the RTT printout, but should probably be disabled for production firmware.

This bootloader does not provide tools to flash the NVM memory by itself. Instead, you can use the flashloader application to perform this task using a CCSDS interface via a UART.

The bootloader performs the following steps:

The application will calculate the checksum of itself if the bootloader CRC is blank (all zeroes or all ones). If the CRC is not blank and the checksum check fails, it will immediately boot application image A. Otherwise, it proceeds to the next step.
Read the boot slot from a reserved section at the end of the EEPROM. It is assumed that the full 128 kB are copied from the ST EEPROM to the code RAM at startup. The boot slot is read from the code RAM directly.
Check the checksum of the boot slot. If that checksum is valid, it will boot that slot. If not, it will proceed to the next step.
Check the checksum of the other slot . If that checksum is valid, it will boot that slot. If not, it will boot App A as the fallback image.

In your actual production application, a command to update the preferred boot slot could be exposed to allow performing software updates in a safe way.

Please note that you MUST compile the application at slot A and slot B with an appropriate memory.x file where the base address of the FLASH was adapted according to the base address shown in the memory map above. The memory files to do this were provided in the scripts folder.