Hi everyone.
I've recently started to look into Arduino Mega Schematic to get a better understanding of the micro-controller and I've come across the D3 diode in the presented screenshot. And I can't understand the function of this diode I've searched in google and read about Flywheel Diode which used for inductors, but not resistors only. I'd happy to be explained what this diode is for.
Thanks in advance 
I'm going to guess it's so the capacitor gets discharged instantly when you lose power, insuring a full-proper reset if power is only lost for a moment (so the processor doesn't crash without a reset).
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See Regression between uno and uno R2 VALIDATED. HARDWARE PROBLEM CONFIRMED for excructating detail.
TLDR: it prevents voltage-doubler-like excursions on the RESET pin that can send the chip into HV programming mode.
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That must have driven a few folks crazy!
Thank you 
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