I thought of that method myself last night, and have already started implementing it. That seems to be the best alternative right now.

I suppose that I need to check the listing file, but I need to make certain that I'm never "blind" for a significant part of a character reception period. I can't afford to miss even one character. There is no pacing. The data stream is coming from a computer, not a human.

I'm thinking that there should be some easy assembly language routine that - upon interrupt, just dumps me to a particular line and starts execution there. As I said before, I don't need to pick up right where I left off. If I'm sending a string, and a character comes in, I can stop sending data and respond to the new request.