Thanks everybody for the feedback.

Most of my projects only have 3V power supply. The idea of using the ICD 
to power the 5V seems like a good idea. I suppose I would add a link to 
isolate the 5V supply
of the micro from the rest of the circuit and remove this only if I need 
to reprogram a protected device.

As long as I can get the bootloader running eventually on all my target 
devices I should not even need to reprogram the actual IC at all and 
upload all through the bootloader. (I use the B7/B6 pins both for ICSP 
and bootloader so they are never connected to any external circuitry).

Thanks again, you guys have helped point me in a direction that should 
provide a suitable solution.

Regards

David

peter green wrote:
>   
>> -----Original Message-----
>> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu]On Behalf
>> Of Gerhard Fiedler
>> Sent: 31 December 2006 13:07
>> To: piclist@mit.edu
>> Subject: Re: [PIC] Code protection for 3V operation
>>
>>
>> Mike Harrison wrote:
>>
>>     
>>>>> The main chips I use are PIC18LF6720, PIC18LF2520 and 
>>>>>           
>> PIC18LF1320. I do
>>     
>>>>> not have a programmer suitable for programming any of these SMD IC's
>>>>> before being placed into the target application.
>>>>>           
>>> Remember that you can program and secure a new chip at 3V, so you could
>>> solder the chips then program in the bootloader on-board. The only thing
>>> you can't do is erase the security bit to reprogram.
>>>       
>> Maybe this doesn't apply to the OP's circuit, but can't you use 5V
>> programming in a 3V circuit? Like making the rest of the circuit 5V
>> tolerant or creating some kind of separation between the micro 
>> and the rest
>> (maybe two solder pads that get closed only after programming). 
>>     
> or just shove a shotkey diode in the power supply to the pic, that way the programmer can drag it up to 5V without effecting the rest of the power net (just make sure anything hanging off PGC/PGD is 5V tolerant).
>
>
>   
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