Using internal modem cards with SCO Xenix

[Ross Oliver]

In article <958 at lakesys.UUCP> davek at lakesys.lakesys.com (Dave Kraft) writes:
>Hi,
>Where I work, we've got two internal modems (can't remember make offhand),
>configured as MS-DOS's COM3: and COM4:, but, when Xenix is started up, they
>aren't listed on the first screen where it lists what you have in your system.
>I can mkdev serial them allright, but when I try to access them with cu,
>it comes back with an error messge like "cannot acces", or something...
>what's wrong here??

It's been a quite I while since I've seen this one mentioned.

The reason you are having problems is that your internal modems cannot
be set to use interrupts other than IRQ3 or IRQ4.  For a serial device
to work under XENIX, it must be configured on its own interrupt vector.
IRQ4 is allocated to COM1, and IRQ3 is for COM2.  Since MS-DOS does not
use interrupts, manufacturers of serial cards have taken the I/O ports
used by COM1 and COM2, and simply extended them on up through the I/O
space, thus producing COM3, COM4, COM5, etc. (I've seen some cards that
claim to go up to COM10).  However, since XENIX requires interrupts as
well as the I/O ports, most of these modems and serial cards won't work
under XENIX above COM2.

However, if you can set these boards to use other interrupts, then you
can use them alongside existing COM1 and COM2 devices.  To do this, you
will have to modify the /usr/sys/conf/master file to tell the serial
driver to handle the additional interrupts.  Modify the "vec3" and "vec4"
columns for the "sio" entry, then rebuild your kernel.

Ross Oliver
Technical Support
The Santa Cruz Operation, Inc.