>The AVR has a PORTn, DDRn and PINn register. DDR sets the data direction.
>PORT sets
>the output status (and is readable, sort of the shadow register that PIC users
>implement in software) and PIN is the actual external signal (inputs as well
>as outputs "overvoted" by a strong signal). As a side effect, it also makes
>the pullup resistors selectable on a per-pin basis (set DDR to input, but
>PORT to 1).
>Very nice that is, and can be found even in the cheapest member of the family.


Indeed..  Set a bit in PORT, then read it in PIN and see if it's high,
gives you a cute way to read capacitance.

And in the AVR, you can execute:

sbi     PORTA,0
cbi     PORTA,0

Without having to insert no-ops like on the pic. This gives a 125nS pulse
on an 8 Mhz AVR.
It's most annoying having to add no-ops into what should be a fast clocked
serial conversation just because the output pin hardware is too slow..