One thing which would do it on the setup I use is if I had it set to
read the file in before programming.  Thus overriding any setup I
had already done.  Can you use a flash part instead.  I use these
almost exlusively for development now.  I just leave the code
protection bit set all the time.  Flash parts are much cheaper than
eprom parts.

Martin

> I have been experimenting with a 16C73B for a couple of weeks with no
> problems and in the last few days I have ruined 2 of them by accidentall=
y
> code protecting them. The first time I thought it had been my mistake, b=
ut
> then I has more carefull and the second one only lasted a couple of hour=
s,
> and I am completely sure about checking the code protection bits before
> eache individual programming.
> So I think this might have something to do with teh programmer (Ider HW =
or
> SW) or somehing about my PC.
> I am using Bojan4s Picall programmer with home made HW on a generic pent=
ium
> 233 PC.
>
> Any ideas on what can be hapening? or what condition should I avoid to
> reduce teh risk of this happening again?
> This is not funy sience this chips cost $40 each here.
> Regards,
>
> Esteban.