Hi Dan,

A question for you about your programming code: does it issue a chip erase before starting programming?

The problem Parviz is running into I believe is because the AT89S53 and AT89S8252 have an auto-erase feature, while the AT89S51 and AT89S52 do not; it would appear the software he is now using doesn't issue the chip erase when the chip is an 'S51 or 'S52. (Maybe it's not checking the chip signature to know just what chip it's talking to.)

Of course with your source he will be able to modify the code to issue this chip erase if it doesn't do it already.

Dennis