Eight bytes in the memory space (200000h-200000Fh) are designated as ID locations where the user can store checksum or other code identification numbers. These locations are readable and writable during normal execution. See the “User ID, Device ID and Configuration Word Access” section for more information on accessing these memory locations. For more information on checksum calculation, see the “PIC18(L)F27/47K40 Memory Programming Specification”, (DS40001772).