[sdiy] Arduino schem - diode in series with R at reset pin?

[Justin Owen]

Hello,

http://i.stack.imgur.com/cPCB4.png

Some of the Arduino schematics have a diode in parallel with the normal R to VRef on the Reset Pin (Pin 1 in the above link).

Can anyone explain what the diode is doing and why it only seems to be on Arduino schems?

FYI, I'm looking specifically at using the Atmega 328P in a non-Arduino, stand-alone circuit.

Thanks,

- Justin