Answers Database

PROM files and programmer checksums


Record #1179

Product Family:  Hardware

Product Line:  1700

Problem Title:
PROM files and programmer checksums


Problem Description:
Keywords: prom checksum programmer

Urgency: standard

General description:

The question often arises as to how one can verify the
correctness of a PROM file checksum.  The answer is that
Xilinx does not disseminate information on checksum
calculation algorithms.  Such algorithms are unique to each
PROM programmer vendor.  They may even diverge from Xilinx's
guidelines on incorporating the reset polarity fields--
for example, Data I/O programmers include the RESET polarity
addresses in their checksum calculations, whereas Xilinx
programmers do not.



Solution 1:


The best that users can do is verify that they get the same
checksum every time they download the same PROM file (for
example, the MCS file, if that is the format they are using),
using the same programmer and version of the vendor's
programmer software.

Short of hand-calculating the checksum itself, there is no
good way to verify that a given checksum is correct.  However,
if you can consistently get the same checksum immediately
after programming the part, as well as when you subsequently
do a read of the PROM's contents, this provides a good
level of confidence that the PROM is programmed with the
proper data.

To ensure that the matching of checksums during these two
steps in the process is meaningful, you must fill
the programmer memory with FF hex both before downloading the
PROM file, as well as before you do a read of the PROM
contents.


NOTE: Makeprom does not calculate checksums.




End of Record #1179