In message  <379487A3827@firga.sun.ac.za> PICLIST@MITVMA.MIT.EDU writes:
> Hi,
>
> > Secondly, I tried programming a couple of the windowed 16C63 devices
> > with the configurations bits set to enable code protection.  Now
> > everytime I try to use them, they are not blank.  I thought these
> > devices were fully erasable, but it would seem I was wrong ? - Have I
> > now rendered these devices totally useless ?
>
> Yep, Microchip covers the code protection fuse with some sort of mask to
> block out UV.  I guess this is to prevent someone from taking a laser and
> clearing only the CP fuse, thus unprotecting the PIC.  I do not know of
> any way to erase that bit now.  (IMHO they should actually have omitted
> the CP fuse in the JW devices since accidents do happen!  You only use
> them for devlopment anyway.)

Niki,

It is very reassuring to know that the same die is used in the JW
parts as in the OTP parts.

Having a different die (ie with the CP fuse) would be a Bad Idea.

Regards,

Mike Watson