STK16C88_08 Datasheet, PDF (10/13 Pages) Simtek Corporation – 32Kx8 AutoStore+ nvSRAM

STK16C88
BEST PRACTICES
nvSRAM products have been used effectively for
over 15 years. While ease-of-use is one of the prod-
uct’s main system values, experience gained work-
ing with hundreds of applications has resulted in the
following suggestions as best practices:
• The non-volatile cells in an nvSRAM are pro-
grammed on the test floor during final test and
quality assurance. Incoming inspection routines
at customer or contract manufacturer’s sites will
sometimes reprogram these values. Final NV pat-
terns are typically repeating patterns of AA, 55,
00, FF, A5, or 5A. End product’s firmware should
not assume an NV array is in a set programmed
state. Routines that check memory content val-
ues to determine first time system configuration,
cold or warm boot status, etc. should always pro-
gram a unique NV pattern (e.g., complex 4-byte
pattern of 46 E6 49 53 hex or more random
bytes) as part of the final system manufacturing
test to ensure these system routines work consis-
tently.
• Power up boot firmware routines should rewrite
the nvSRAM into the desired state. While the
nvSRAM is shipped in a preset state, best prac-
tice is to again rewrite the nvSRAM into the
desired state as a safeguard against events that
might flip the bit inadvertently (program bugs,
incoming inspection routines, etc.).
Document Control #ML0018 Rev 2.0
10
Jan, 2008