AVR-Chat

Not 100% sure but it looks like using ICP on the Butterfly is out, 
whats a useful alternative for decoding PWM? External Interrupt pin? 

I hope I'm answering my own question correctly - would designating a 
pin as an external interrupt be appropriate? 

From datasheet from ATMEGA169. Given - 
"The INT0 interrupts can be triggered by a falling or rising edge or 
a low level. This is set up as indicated in the specification for the 
External Interrupt Control Register A – EICRA. When the INT0 
interrupt is enabled and is configured as level triggered, the 
interrupt will trigger as long as the pin is held low." 

This doesn't look a whole lot different to using ICP? 
Anyone? 

Thanks in advance, 
Adam