I appear to have several CY14B108N that are repeatedly performing partial autostores to the lower addresses during powerdown even though the autostore has been software disabled. I have others that repeatedly work properly so I am confident that I am disabling correctly. I am also fairly confident that I am not accidentally triggereing the HSB pin to perform a hardware store. What else is there to check? My thought is that these devices have something wrong with their disable autostore circuitry, but how likely is this? Is this feature electrically tested before delivery? What else should I check that could interfere with the disable autostore and allow a partial autostore to the lower addresses to take place during powerdown? Also, since my lower addresses appear to be affected, how does the store occur across the addresses? Is the entire memory written at virtually the same time, or are the addresses sequenced starting at #0?
I now have collected more data on 50 devices selected from two different lots.
Of the 50 devices tested:
8 overwrite the lower half of the memory.
11 overwrite the upper half of the memory.
31 work as expected and do not perform an unauthorized store.
Is anyone else testing this? Has anyone else seen this?