For teaching purposes, I'd really like Ports 2 and 3 on my Altair to be 88-SIO ports connected to a dumb terminal and a paper-tape punch respectively, leaving Port 1 as a 2SIO port for taking supervisory control of the Altair via a laptop and a USB/Serial cable. What I want to teach is the low-level control of the ports (as in the early video of the keyboard being echoed to the screen) and the 88-SIO mode seems easier for teaching that than the 2SIO mode (which has lots of options I don't want to introduce to the students).
But I'm right in thinking that we can't have Ports 2 and 3 both be 88-SIO ports aren't I? Whenever I try setting the second one of these two to 88-SIO the other one flips back to being 2SIO.
Assuming I can't have Ports 2 and 3 both being 88-SIO ports, could someone tell me the simplest machine code instructions for setting up one 2SIO port to be, say, 9600 baud 8N1 and then another be 300 baud 8N1? Once they're set up, presumably all I need to do is keep polling a single bit in the control word--looks like its bits 0 and 1 instead of bits 0 and 7 as I do with 88-SIO--and all else is the same one the port is set up. I've got the 2SIO manual in front of me and the number of options (to do with setting the baud rate in software) is bewildering.
I don't mind which two ports I have as the easy-to-program 88-SIO ports: it could be Port 1 and Port 2 if only I were allowed use Port 3 for the Configuration Monitor, if that's possible.
Regards
Gabriel Egan