>I've two windowed 12C508's with the code protection bit set. Are they
>destined for the scrap heap or not? I erased them overnight, and was
>able to program them, but when I placed them in a circuit in which
>the OTP version works fine, I have no joy.

Try covering the window.  The chips are very sensitive to light.

FWIW, this is a very useful time to have those old black write-protect tabs
from the ancient floppy media.

Andy

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Andy Kunz - Montana Design - 409 S 6th St - Phillipsburg, NJ 08865
          Hardware & Software for Industry & R/C Hobbies
        "Go fast, turn right, and keep the wet side down!"
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