Microport serial communications

[Wolf N. Paul]

(I have cross-posted this follow-up to comp.unix.microport, as it is more
appropriate and more likely to find expert readers there.)

In article <112 at cosi.UUCP> bill at cosi.UUCP (Bill Michaelson) writes:
>
>Another annoying problem (unrelated to Merge): I have four serial ports
>on my '386 machine.  As is typical with many AT clones, the ports may
>each be configured to one of four addresses (called COM1-COM4 in the MS-
>DOS world), and one of two interrupt levels (IRQ2 and 3).  The device
>drivers that come with the system apparently don't allow serial ports to
>share interrupt levels.  It's puzzling because the documentation indi-
>cates that multiport boards use single interrupt levels.  A command
>called ttypatch is used to configure the drivers.

As it was explained to me, the problem is the following:

The driver will support multiple ports (at different addresses) using the
same interrupt IF THEY ARE ON THE SAME BOARD. In other words, two ports
may share an interrupt, two boards may not.

Unfortunately, standard AT and XT style com boards, which support two ports
per board, are set up to use two interrupts per board, and both of these
may be shared by up to two boards. Thus, it is set up the reverse from what
the Uport serial driver expects.

The Uport release notes explicitly refer to "Digiboard and similar" boards;
I didn't see that reference until after I got frustrated myself with the
same problem.
-- 
Wolf N. Paul * 3387 Sam Rayburn Run * Carrollton TX 75007 * (214) 306-9101
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