Hello all,

Lee Jones wrote:

>>Out of curiosity, if the chip is code protected, will the attempt
>>to bulk erase unprotect the chip?
>>If yes, then it is definitely a grand goof-up of major concern!
>>If not, then, it's good to know that code remains protected.
> 
> 
> Out of experience, no.  Chip stays code protected.  It seems to
> reprogram properly (at 3.3 volt) but the verify always fails.
> 

I just tried the same thing, and got some strange results.  Blank check 
failed, reprogramming verified (!) but didn't work correctly (!).  Still 
code protected.

The only way to successfully erase a code-protected chip is to run at 5V.

For my 3.3V development, I turned code protect off, and now it seems to 
erase ok - at least the program space.  Sometimes EEPROM/config bits 
fail.  But so far I can do normal development work without constantly 
switching the PIC Vdd power.

Bottom line:

If code protect is on, the 18F parts are effectively 
one-time-programmable in a 3.3V system.

If code protect is off, it seems that it can be erased at 3.3V, with 
occasional flakyness.

> Following paragraphs sum up a bunch of non-billable labor when I
> had to figure this out for myself a while back.

This is *EXACTLY* the problem.  Microchip didn't spell out this weird 
exception to their whole low-voltage in-circuit everything system, and 
experienced engineers, on the clock (or working for zero, if freelance) 
have gotten burned and customer money wasted and schedules missed.  Its 
not like nobody at Microchip knows about this, they just want to keep it 
under the rug.

J

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