> 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). Then
> supply
> the micro with 5V from the programmer.
>
> Gerhard
>

Do programmers hold the chip in reset prior to applying the +5V? If so, it
APPEARS that all circuitry going out to the 3V circuitry would be
floating, and not pulled up to 5V when the supply is increased for
programming. I've done the diode trick and put both the PIC Vcc and the 3V
supply on the programming header. The programmer is not connected to the
3V pin, but does drive the PIC Vcc pin. Once the system is programmed, we
put a "programming jumper" between these two pins so the PIC gets the full
3V.

Harold


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