I don't think this is my problem as an experiment I did showed a possible
clue as to
what is going on.

        1- erased a '508 JW part
        2- put a brand new OTP (so it is blank) '508 into my programmer and
           read in the contents.
        3- programmed the JW part with the contents of the blank OTP part
           Both chips still show up as erased.
        4- programmed my target code into the JW part
        5 - plugged the JW part into my target circuit and NOTHING happens!
            Note that the EPROM windows was not covered in case ambient light
            was helping me out before (which shouldn't matter, I'm doing nothing
            fancy with the chip).

        6 - Took another freshly erased '508 JW part and programmed it with
my code.
            Plug this chip in the circuit and it works fine!

  The only thing that stood out is that memory location 1FFF contains the
OSC cal number.

For the OTP parts when blank and read, this number reads CA0 or C80 or C90
depending on the chip.

When the JW part is read in blank, location 1FFF reads 000.  Even though
both the OTP and the JW
part when blank have a different 1FFF value, the programmer says both are blank.

When the  completely blank JW part is programmed with the target code, 1FFF
contains A32 (previous value 1FF).
When the OTP part is programmed with the target code, 1FFF contains the same
value it held before
programming (like CA0).

The programmer says that both chips verify okay.  WIERD!!

Dave


>        I think it has something to do with the initialization of memory
registers
>before a read.  For example; do not count on the fact that a register will
>read a `zero' before you have written one in there!
>p.s. You might want to check the microchip web site, I remember seeing
>something about it there.
>