STK15C88
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.
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:
• 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.).
• 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,
Rev 2.0
Document Control #ML0016
Jan, 2008
10
SIMTEK [ SIMTEK CORPORATION ]
