Hi,
What will happen to data comming in via serin2/debugin if the usart triggers an Interrupt?
Depending on the oscillator speed, how tight your ISR is and the baudrate of the incomming data captured with SERIN2/DEBUGIN you may or may not be able to capture the data properly, hard to say for sure...

What will happen to data being transmitted via Serout2 or debug out if the usart triggers an interrupt?
Same thing, the SEROUT2 command will get interrupted and thus its timing will be messed up possibly too much for the receiver to capture properly. Again, it MIGHT work depending on execution speed, baudrate etc but I can not say.

Will it jump out of the serin2/debug in and return into it correctly or will it retun to the next command.
It will jump out of the command and then back into the command (not to next command (if it wasn't finished)) as if nothing happend. However, the time spent in the ISR will be "lost" so the timing for the bitbanged commands will be off by that amount which may or may not present a problem depending on things outlined earlier.

/Henrik.