Hi all,

I've just joined the list after an hiatus of a few years.

I'm just laying out a board with a 16C877 on it and I've included the RJ
connector so I can use the PIC-ICD for programming and debugging.  I've
got a couple of MCP2510 CAN devices all attached to the MCLR line for a
common reset.  As I started the layout I realized that the programming
voltage used to put the device into High Voltage Program mode would be
passed onto the other devices.

What I've done is connected a 1K to the MCLR pin and a 47K pull-up to
Vdd on the other end of the 1K resistor.  I've also put a 5.1V Zener
there.  That line can now go out to the other CAN devices and a switch
to ground while the RJ 6 pin Vpp line goes directly to MCLR on the
processor.  This should allow the 13V signal to show up at the processor
for programming but drop it down to 5.1V max at the other end of the 1K
and therefore to the rest of the circuit.

I can't really think of any other way other than two Reset circuits
joined at the inputs by the pushbutton but each one driving either the
PIC or the rest of the RESET circuit.

Any other suggestions?

Thanks,

John

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