> Van: Steven Keller <keller@theramp.net>
> Aan: PICLIST@MITVMA.MIT.EDU
> Onderwerp: EPROM erasing question
> Datum: vrijdag 6 november 1998 18:15

Hello Steven,

> Is it possible for an EPROM (16C63) to check out as blank, program, and
> verify correctly but not be fully erased?

Yes.  It depends on the time between Erasing and Programming the part.  If
you take a part directly outof a (working :-) Eraser and than Blank-check
the part it could show up as erased, but some minutes later it could fail.
I'ts sort of "bouncing back". That's why (combined with other reasons) most
people "over-erase" EPROM memory.

If you do experience "strange" behaviour, try verifying the part.  If it
fails you could be experiencing "bounce back".  By the way ... Do you
verify with 6 & 4 volts or with 5 volts only ?  (PicStart + only verifies
with 5 volts.)  "Professional" programmers check with 6 & 4 volts to have a
bigger error-margin.

Greetz,
  Rudy Wieser