I use 18F8722s exclusively and I need to calculate a simple checksum to add all the bytes from Flash ROM locations 0x18 to 0x1FFFF together into one 16 bit word.

READCODE is only useful in the lower 64K of memory, so that won't work.

Does anyone have an assembly-language subroutine that would calculate the checksum and pass the result back to PBP?