Oh yes you are right. If the PIC is powered from the board, then one has
to control the Vdd from the board (switch off the power) so it may not
be possible at all. This is true for any programmers. I think Wouter
has a good explanation last time. For example, PICkit 1 is able to
program the 12F629 with internal RC oscillator and internal MCLR
because it also control the target power. It is a programmer cum
target board.

However ICD2 does not even program a standalone 12F629! We need to
check the hardware ICD2 in order to see if it is really a hardware 
limitation or a firmware bug for the original ICD2. For some cheap
clones, this may really be a hardware limitation.

Regards,
Xiaofan

>From ICD2 help file:

ICDWarn0033: You have selected Internal MCLR and Internal Oscillator
in your configuration settings. If your code makes use of port pins
that correspond to Clock and Data pins in programming mode, you may
not be able to reprogram your device. See on-line help for this
warning for more information. (OK/Cancel)

When Internal MCLR is used with MPLAB ICD 2 for programming, both Vpp
and Vdd are powered together, and then Vpp is pulled high to Vihh to
enter programming mode. This means that your code will be running
before Vpp goes to Vihh. If that code makes use of port pins that
correspond to Clock and Data pins in programming mode, there is a
chance their values may not be 0, as necessary to enter programming
mode. Therefore, the device could not be reprogrammed.

Click OK to continue programming or click Cancel to cancel the
programming operation.

Work-Around 

When External MCLR is used, this is not a problem, as Vpp can go
directly to Vihh. Also, if External Oscillator is used, the external
oscillator can be kept from running, thus keeping the code from
running, until Vpp is at Vihh.




On 9/11/05, Gerhard Fiedler <lists@connectionbrazil.com> wrote:
> 
> I'm not sure how it would do that if set to external Vdd. I regularly
> program boards with the ICD2 where the PIC is powered from the board. The
> ICD2 simply can't control Vdd in this setting.
> 
> 
> FWIW, we never had problems with programming the 16LF88 (external -MCLR)
> with the ICD2 in-circuit. We did have problems using a clone sold here in
> Brazil in this application, though.
> 
> Gerhard

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