Hi,

I have a question re: ICSP, that I can't seem to find and answer for=20
anywhere...

I'm trying to setup ICSP for a circuit, such that the programmer can stay=
=20
connected during operation of the application circuit, and all I would ne=
ed=20
to do is disable power to the circuit before programming.  Then just swit=
ch=20
the power back on and the circuit should operate with the new code.

To properly set this up, I should have a diode from the output of the 780=
5 to=20
the Vdd pin on the PIC.  See...
    http://www.narwani.org/neil/stuff/Tait_ICSP_1.3.gif
(I've only shown the relevant parts of the ckt.)

However, I really need to have 5V at Vdd.  And changing to a higher-volta=
ge=20
regulator adds different complications.  So I've come up with this...
    http://www.narwani.org/neil/stuff/Tait_ICSP_1.4.gif

The PIC will get Vdd during programming from the app circuit's own 7805. =
 I=20
can't see why this won't work, except that the 7805 may not switch on fas=
t=20
enough.  The only capacitors I have on the 7805 are a .1uf from Vin to=20
ground, another .1uf from Vout to ground and a third .1uf bypass cap from=
=20
Vout to ground at the PIC pins.

Can anyone tell me if this will really work?  Or if there is a better way=
 to=20
accomplish what I need?

Thanks,
-Neil.

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