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 True USB Willem Programmer (GQ-2X, GQ-3X, GQ-4X)
 Problem with ST M27C256B
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Posted - 05/01/2008 :  22:15:02  Show Profile  Reply with Quote
Trying to program ROM code into a several UV erasable ST M27C256B chips. Programmer is a GQ-3X Re-1.00. I select the exact chip type, blank check, load the bin file and program. Every 128th byte does not program. In other words, $7F, $FF, $17F, $1FF, etc, are unprogrammed (data value = $FF). The only exception is the LAST byte in the buffer, $7FFF, which programs fine.

This seems to only happen with ST M27C256B devices. I tested programming the same BIN file into a TI TMS27C256 and a Microchip 27HC256 and both programmed just fine. I have tried programming 6 different ST devices, 4 of which were brand new from the manufacturer. All had the same problem. I have also tried lowering the speed, doing a double write, and changing devices to the generic 27C256. Each time the results are the same - I cannot program the ST devices.
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2926 Posts

Posted - 05/02/2008 :  16:46:03  Show Profile  Reply with Quote
For some batch of M27C256B production. Add a 1K resistor between chip pin 20(CE) and pin 14(GND) will help to solve the problem.
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