Frank,

PROM Checksum provides two very important functions;
1) explicit revision control;
2) mission critical validation.

As Troy indicated PROM validation is performed to validate the integrity of a PROM in systems that are intended to do no harm and who's explicit status and capability must be known.

Less dramatic but equally useful is the checksum as the final validator of a PROM's revision status. Programmers generate checksums for the code downloaded. If this checksum is re-iterated upon the prom label and is available for query (manual on display or otherwise communicated) and certain revision characteristic can be determined.

Our devices communicate their rev' levels (using checksum) when they transact.

regards,
p