> I haven't figured out why, but when I read a brand new PIC for the first
> time it reads 0000's.
>
> Once a new "F" series chip is purposely erased, then it will read all
> 1's.
>
> This even happened on some older 16C74-JWs that I had. It's like the CP
> fuse is set on a new chip. I could not program these chips with a
> PICstart and found that I could after erasing them initially.

This surprised me, so I did some tests.  I looked around here for
unprogrammed 16F parts, and found some 16F84, 16F628, 16LF628, 16F876, and
16F877.  Of these, all except the 16F628 read back as all zeros.  I tried
several 16F628s and the ones that weren't previously programmed read back
all ones.  We never explicitly "erase" F parts, just toss them back in the
bin when done, so a used part would never be all ones or all zeros.  Just to
make sure I wasn't going nuts, I checked an erased 16C66 and it did read
back all ones as expected.

I ran these test from MPLAB using a PicStart+, each time changing the
project settings for whatever chip I was testing.  And yes, I made sure the
16F628 was plugged in the right way around.  I even tried several of them.

This surprises me even more than all of them being zeros.  Can anyone else
reproduce these results?


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