Hello all,

I have decided in my application to use half a dozen 16F84's to interface
to a bunch of components.

However, space is very limited, so I want to use the surface-mount version
of the chip. I plan on programming them in circuit, and will provide a
four-pin header for each chip on the board. I plan on using RB6 & RB7 only
for programming, and so will not need to isolate them from the circuit
(since they will only go to the pins on the header).

The question is, how do I isolate Vdd? I was thinking along the lines of
running a trace from the Vdd pin directly to the power header pin, and to
the rest of the circuit through a diode. The diode would be mounted to
allow current to pass into the chip from the circuit power supply, but not
from the chip to the rest of the circuit when powered from the programmer.
Presumably, since the voltage drop would be about 0.6 volts, the power
running into the PIC from the 5 volt circuit supply would end up being 4.4
volts,  which is well within the limits.

Will this work? Is there a better way?

Thanks in advance...

Later,
Jon

--------------------------------------------------------------
   Jon Hylands      Jon@huv.com      http://www.huv.com/jon

  Project: Micro Seeker (Micro Autonomous Underwater Vehicle)
           http://www.huv.com