Hi Ijaz,

There's more to programming a device than just the algorithm. Some devices need an external Vpp voltage which should comply with rather strict demands. I think the most likely reason for the failures Erik's talking about is that the Vpp voltage was not optimal. Voltage too high or too low, overshoot when switching it on; these things can all contribute to reduced reliability of the memory.

So the difference between a home made programmer and a professional one may just be careful PCB layout.

Rob.