Seems like they could have added a bit "code protect disable".  When this
fuze gets blown, you can nolonger code protect.  This would allow us to
make the chip "un-protectable" for development and still be able to protect
them for production.  If the code protect is enabled before code protect
disable, then the chip would forever be code protected.  If the code
protect disable was "enabled" before the code protect, the chip would be
un-protected forever.  Both bits should be un eraseable.

Any thoughts.

Norm

At 06:34 PM 2/12/97 +0000, you wrote:
>On Thu, 13 Feb 1997, Mike wrote:
>
>> >David,
>> >
>> >   Not that it is any consolation but I am looking at 3 PIC16C62A/JWs
>> >   out of a group of 5 that I had been using.  These 3 all mysteriously
>> >   got code protected.  Even though I have been especially careful and
>> >   am using a Microchip Promate programmer, it still happened.
>>
>> I understand that on HC705 series any code protection is via EPROM bit,
>> I infer that code protection on PIC is via a fuse and therefore cannot
>> be erased by UV ?
>
>Yeah I'd imagine so !
>
>>
>> Does this also apply to the flash parts - wouldn't it be more efficient
>> that the code protection be via EPROM type bit anyway ?
>>
>> Are there any moves by microchip (hi guys) to change to EPROM bit ?
>>
>        I hate to say it but  I recon judging by previous discussions I
>have heard that the move was actually in the other direction. I reckon
>that it may have been due to a worry by microchip that one may be able to
>selectively erase parts of the windowed chip using perhaps a fine laser
>beam or something. And by doing so only wipe the CP bit.. I.e. exposing
>the protected code..
>        I am no expert on the subject so all I have just said is purely
>hearsay. Please correct me if I'm wrong in those assumptions.
>        However on the note of Microchip doing something about the problem
>I would suggest and hope I'm taken seriously that a variant of the
>windowed chip be produced that has no code protect bit.. Surely this
>wouldn't be difficult (I realise Chip changes incur fabrication costs )
>but I believe there would definately be a large market for such chips as
>most developers have no need to code protect their windowed versions..
>It's easier to lock them in your drawer ! Could anyone who agrees with
>this suggestion please voice your support to confrim such a market.
>
>
>
>
>
>> And in any case since I hear that all code protected PIC parts are just
>> as easy to read as the code protected motorola parts - wouldn't it be
>> logical that a code protect chip could be erased and reused ?
>>
>
>        Hmmmm, Are you sure on that one ? I'm sure microchip wouldn't be
>impressed !
>
>> Rgds
>>
>>
>> Mike
>>
>
>
>                                        Dave.
>
>
>
>http://www.csn.ul.ie/~david
>
>