In most cases you can do ICSP with the PIC
permanently powered up. I do a lot of my
projects this way using a PicStart Plus.
When not programming, the PSP keeps the
PIC in reset, (MCLR low) it then goes to
MCLR at 13v to do the program and verify etc.

If you add a switch on MCLR to connect it
to 5v instead you can simply flip the switch
and run the program in the PIC.

I have one of these setups on a protoboard
(the white plug in ones) and can just leave
MPLAB running, flip the switch, press "program"
on MPLAB and then flip the switch back to run
it. Very cheap setup and great for small PICs
(16F84) in development.
-Roman




Anand Dhuru wrote:
>
> Ron, I faced precisely the same problem with my EPIC programmer. The
> solution might sound horrendeous, but is actually safe, and proven to be
> working fine.
>
> The EPIC uses a transistor to switch the +5 volts to the PIC only during
> read / write ops.
>
> In my case, since the target circuit had very few components besides the PIC
> itself, I wanted to power it up with the 5 volt regulator on the EPIC
> itself. This did not work reliably, exactly as what you have described. The
> solution was to short the collector and the emitter of the switching
> transistor. I realize this sounds wierd; the transistor is now apparently
> serving no purpose. But it works like a charm. Even resets the PIC after
> each write cycle.

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