We have been using The Philips version of the RD2 8051 chip for a while with no problems. As they don't seem to be made any more, we moved to the Atmel equivalent (part number on the chip: 89C51RD2-IM, notice no "T")
However, we are having problems trying to program the Atmel chip using the serial Intel hex ISP protocol. We never had any problems when progamming the Philips part using the same programmer (a custom made unit)
The only change we made was to reduce the programming voltage from
12 volts to 5. The PSEN, ALE and EA lines are all exactly as required for the Philips part.The programming software when run seems to work OK, The echoed full dot codes '.' are returned by the chip on every hex sequence sent as they should. However, when attempting th read the contents of the chip back, program EPROM locations 76 to 7F never seem to program correctly, they are stuck at FFhex. We have tried a batch of five Atmel chips, they all do exactly the same.
Are we doing something wrong? Are there any essential differences ebtweeen the Philips programming method and the Atmel one that we should be aware of??
I don't think it is a problem with the Atmel part. The real question is: is there any difference between the Philips andthe Atmel programming methods that may be causing this??
Thanks in advance
Ted