1.9.1 Bootloader Application Verification Method - Not Blank

If the "Not Blank" verification method is chosen, the bootloader will verify that the application image space is completely unprogrammed. This does not check the validity of the application image. It only verifies that something has been programmed into the application space reset handler. It does not check for any types of errors in flash memory.

This form of verification is very quick and results in very fast entry to the application from the bootloader. It does not provide any error detection capability. It can't detect if an invalid firmware image was loaded or if the memory has corrupted since being programmed.

Implementation Details  

In the implementation provided only the application reset address is checked to make sure that it is not still in the erased state.

To strengthen this verification a bit more, the Unified Bootloader Host Application (UBHA) software package was updated for the 16-bit devices to program this address last of all the program memory. This way if a firmware image is partially loaded but gets interrupted before it completes, the reset address will not be programmed and the bootloader will refuse to jump to the application. If a new host application is created for use with this firmware and this verification method is used, it is suggested that a similar approach is implemented.