From: arthur@ptt-iat.uucp (Arthur Donkers) Subject: Re: Multi-Port Serial boards Date: 3 Sep 1993 09:42:02 +0200
In article <2655a4$dl5@nic.umass.edu> ranger@titan.ucs.umass.edu (Net Ranger) writes:
>[ Article crossposted from comp.os.linux.help ]
>[ Author was ranger@titan.ucs.umass.edu ]
>[ Posted on 2 Sep 1993 14:38:03 GMT ]
>
>I read the Serial-FAQ... but I am unclear on one point, is it possible to
>run multiple serial ports (like 8 or 16) using one of the "supported" cards
>listed in the FAQ without running into IRQ problems under linux?
The supported boards might work. There are two possibilities :
- A board (up to 4 ports or so.) can set an IRQ per port (the STB can do this)
This means you loose an IRQ to each serial port configured.
- A board might share interrupts. The kernel then polls a flag register (or
each connected port) to determine which port generated the interrupt. The
kernel supports this (p10 and up ???) for the standard DOS (yuck) COM ports.
To implement you need to kludge around with diodes to make a wired OR so
one IRQ doesn't blow out the other IRQ (check the postings from a few day ago
it contains a diagram on how to do this).
A last word :
Be carefull when buying a BOCA board. Some models don't support all necessary
hardware signals (CD is missing) so they can't be used comfortably for dial-in
access. They might work with terminals though.
Just my $0.03,
Arthur
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