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