pmartin@psmsd.UUCP (Paul Martin) (07/24/90)
I know this has been asked many times before, but I never really paid any attention because it never applied to me, but does anyone out there know of a way to use COM3: and COM4: ports on a standard multi i/o board with xenix (ie a tty device)? COM3: shares the irq with COM1: COM4: shares the irq with COM2: These ports work fine under dos, but I would like to really use them under my Xenix/386 v2.3.2 I think it would just be a simple mknod but I don't know the major/minor device numbers Thanks in advance -- +--------[ Paul Martin at P.S.M. Software Development ]--------+ | Smart: pmartin@psmsd.UUCP | "Yes I am serious, and don't | | Dumb: ...uccba!psmsd!pmartin | call me Shirley!" | +-------------------------------+------------------------------+
scott@clmqt.marquette.Mi.US (Scott Reynolds) (07/26/90)
pmartin@psmsd.UUCP (Paul Martin) writes: >I know this has been asked many times before, but I never really paid any >attention because it never applied to me, but does anyone out there know >of a way to use COM3: and COM4: ports on a standard multi i/o board with >xenix (ie a tty device)? >COM3: shares the irq with COM1: >COM4: shares the irq with COM2: I asked myself this question some time ago, and I dug into the docs with my system (an old, old XENIX, much like SCO XENIX/286 2.2). I used tty drivers from my own manual plus a couple I picked up elsewhere and came to the conclusion very quickly that sharing interrupts just won't work on an ISA bus because the IRQ lines can apparently support only 1 device at a time properly. What I did was hack on the drivers a lot to add a few features I needed and support 4 ports by using IRQ 4, 3, 5, and 2 (in that order for DOS addresses COM[1-4]:). The last port shares IRQ2 with the 80287 and the HD controller through a slave interrupt controller, eliminating the type of conflict you have with sharing any of the other IRQ lines. [In case anyone is interested, on my IBM PC/AT and this old XENIX I ended up having to use interrupt 0x19 for the port set on IRQ2.] I'll mail copies of the 8250 tty driver to anyone who would like to see it. -- Scott Reynolds = scott@clmqt.marquette.Mi.US Enterprise Information System = ..rutgers!mailrus!sharkey!clmqt!scott "Where were you when I laid the earth's foundation? Tell me, if you understand." -- YHWH (Job 38:4)