Reyes wrote:
>
>EPicwin does not allow an erase only, just allows erase before programming,
>so I cant verify erase.  I found out that 0091 is the location of first
>code
>change.  That is overwrite goes ok until 0091 where the first different
>value is encountered.
>I verfied that vpp during programming is 12.6 V.
>
>Thanks for the reply and any further thoughts would be appreciated.
>

Two points:

1. The 12c508 is an OTP chip.

There is no erase function (except for JW devices in a UV eraser). Code
changes can only overwrite 1's to 0's. Once a 0 has been programmed in any
location, you cannot overwrite it with a 1.

2. Your Vpp at 12.6 volts is under spec.

According the programming spec, 12.75 is the minimum. Microchip recommends
programming at 13.00 to 13.25 volts.


Regards, Bob

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