Hmmm...  I tried setting MCLR to RA5 instead of MCLR, and now the chip
totally refuses to program.  Now I can't change the config bit back to
MCLR  :-(

On 5/9/05, Alan B. Pearce <A.B.Pearce@rl.ac.uk> wrote:
> >I am having a problem using the ICD2 as a programmer and debugger.  I
> >am using a PIC16F87, running on a PICDem 4 board.  This problem only
> >occurs with one project.  After the program has been run, the power
> >needs to be unplugged for a second before the PIC will program again.
> >If I don't unplug it, it says that when verifying the code, 0 was read
> >instead of the expected value.  When using the ICD2 as a debugger, if
> >the power isn't unplugged before programming, it says the target
> >device ID is 0.  I am using the ICD2 with USB, and supplying power to
> >the target board, not through the ICD2.
> 
> I have a feeling this is a problem with certain devices, especially when the
> MCLR line is configured as an input. The problem arises because to go into
> programming mode the PIC needs to have MCLR at Vpp before Vcc is applied.
> Check the data sheet for your chip - or more especially the programming
> spec.
> 
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