If you use the MCLR as an input, you will need to turn VCC on and off at=20
the right time to get into programming mode. (VCC off, MCLR to VPP, VCC=20
on)  From your schematic, it does not appear that the programmer=20
controls VCC.
Also, a 1K resistor between ground and the switch common should allow=20
programming in any switch position.

Kerry



David wrote:
> All,
>
> I am designing a small board with a 12F and need to use the=20
> ICSP_CLK/ICSP_DAT and MCLR as inputs.  Apparently there is a Microchip=20
> appnote about this, but I have been through the website and cannot seem=20
> to find it.
>
> Using the right config bits is assumed (i.e. so it does not need MCLR to=
=20
> run).
>
> The input is a rotary switch with the common to GND.  I plan on using=20
> the PIC internal weak pullups (the proposed circuit is at=20
> http://edeca.net/temp/electronics/PCB0016.pdf).
>
> Using these pins for the switch selector means I can upload a modified=20
> firmware that doesn't read the switch to do ICD.
>
> Obviously I'll have to set the switch to 0 to disconnect it from GND=20
> before programming, but are there any other problems with this as an idea=
?
>
> David
>  =20

--=20
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