[sdiy] 4006 on evilBay

[Colin f]

> I don't think the open drain outputs count as standard GPIO. 
> If you look at the datasheet for the PIC 16F627A (just an 
> example - I know this chip has an OD output) the diagram (fig 
> 5-4) for the RA4 port pin shows no protection diode to Vdd, 
> only Vss.

Datasheet shows Vmax at RA4 of 8.5v (page 140)
Which might just be enough, with a zener diode to regulate the open-drain
pull-up voltage, to tip a CMOS input on a 15v supply to the high state...

Cheers,
Colin f