Dro Kulix wrote:
> Hiya, folks...
> 
> I have an application circuit including a PIC16F88 and a 20MHz crystal 
> set up on a breadboard.  The circuit works, but the PICkit 2 programmer 
> I'm using won't recognize or reprogram it as-is.  By process of 
> elimination, I've found that the programmer consistently works when the 
> crystal is removed, but consistently fails when the crystal is in place.
> 
> The crystal is connected to the CLKI and CLKO pins, each with a 22pF cap 
> bridging to ground.  Both the application circuit and the programming 
> problem remain unchanged whether or not the caps are present.
> 
> The workaround I'm currently employing (remove/replace as necessary) 
> will cease to work when I've moved from the breadboard to something more 
> permanent.  Is there something I can do to get the Pk2 working while the 
> crystal is still installed?
> 
> Thanks
> dro

Shooting from the hip here... it sounds like your reset line comes up 
too slow at programming time.  If so, then the crystal takes off and the 
program counter advances beyond 0x00.  Remove the crystal and now it 
programs ok.

What sort of reset circuit do you have?

Also watch out for massive capacitance on the power supply line.  Some 
programmers have trouble with that one also.
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist