schoff@bbn-unix@sri-unix.UUCP (08/31/83)
From: Martin Schoffstall <schoff@bbn-unix> I bought a quadram board with 2 RS232 ports on it, why can't I use both ports? Even worse, I have two quadram boards if I enable COM1 on one and COM2 on the other it doesn't seem to work either? any suggestions? schoff at bbnu
BILLW@sri-kl@sri-unix.UUCP (08/31/83)
Some boards do not enable interupts for the second rs232 port. I tried this out as I was developing a (comercial) communications package for the IBM PC, and found that the interupt pin on the second 8250 on a (argh! cant remember the company name. It was a 256K memory + 2 serial port board) wasnt connected to ANYTHING! The reasoning behind this (I assume) is that if you have multiple chips generating a single interupt, then you cant trivially figure out which port the interupt was actually for. In particular, interupt driven software that assumes only one active port is likely to break. Bill Westfield