Doug Bell dbell at nxtv.com
Thu Aug 11 18:27:42 CEST 2005

I am trying to use the PMC4 on the EPIA-SP ( vt8237 ) but can't write to
the internal flash. 

I have code that can read and write successfully on a SST49LF004
installed in the top socket. However, when I throw the switch to the
internal flash (PMC Pm49FL004 ) I can read the flash ID via the
registers at ffbc0000 and 0001, but I can't read the ID via the typical
jedec cycle. Interestingly ( or not ) I seem to read back the last byte
written out in my code, e.g. a 0x90 0x90 is read as the ID after
completing the sequence to enter product ID mode ( which ends with a
write of 0x90). 

I tried adding various sleeps to rule out timing issues. I am assuming
the vt8237 is operating in LPC mode as opposed to FWH; the datasheet for
the Pm49LF004 mentions it is read-compatible for FWH. I find it curious
that the 0x90 I mentioned above is the same BYTE i wrote out, rather
than some nibble-based variation like 99 or 00 (since LPC bus is 4
bits ). 

Any insight would be greatly appreciated. Thanks, Doug

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