Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uwm.edu!srcsip!jhereg!quest!digibd!tjc
From: tjc@digibd (T. J. Carter)
Newsgroups: comp.sys.ibm.pc
Subject: Re: DigiBoard MC/X interrupts?
Keywords: DigiBoard
Message-ID: <1990Mar20.191049.15494@digibd>
Date: 20 Mar 90 19:10:49 GMT
References: <53516@microsoft.UUCP>
Organization: DigiBoard Incorporated, St. Louis Park, MN
Lines: 48

richgi@microsoft.UUCP (Richard GILLMANN) writes:

>I've been trying to get some interrupt driven code to work
>with the DigiBoard MC/8 board and not having much luck.  The
>MC/8 board has eight serial ports on it plus some hardware that
>provides a status port, which one can use to tell which port
>generated an interrupt.

>I have code (essentially the same as COMPKG2 from the Info-IBMPC
>archives) that works fine with the regular AT bus DigiBoards,
>and also works fine with the regular two PS/2 serial ports, but
>it doesn't work with the MC/8.  (The MC/8 is the PS/2 MCA bus
>equivalent of the DigiBoard Com/8 card).

>What happens is that as soon as my code enables the Interrupt Enable
>Register for transmit interrupts, the machine hangs.  It never
>gets to the interrupt code.  The DigiBoard tech support folks don't
>seem to know much.  Has anyone had this same problem and figured it
>out?  I'd sure appreciate a clue.

>Richard

I think the blunt of your problem is that the DigiBoard MC/8 uses a
different interrupt register scheme then the COM/8.

The Com/8 interrupt status register
delivers the channel number of the interrupting UART in bits 0-2, with
a 000 representing port 1. This value is often used by software as an
offset into a jump table. When no interrupts are pendind a value of 0xFF
is returned.

The MC/8 uses an entirely different scheme. The MC/8 uses one eight bit
register to simultaneouly represent all of the channels interrupt status.
Bit 0 is used to indicate channel ones interrupt status, bit 1 channel twos
interrupt status and so on. When a bit is set there is a interrupt pending
on the cooresponding channel. A value of 0xFF indicates interrupts pending on
all eight channels. The values returned by the MC/8 interrupt status 
register are not useful as indexes into a jump table.

I am sorry to here that our tech support people were not able to help
with this. If you have any further problems feel free to call and ask for
me, I should be able to answer any questions.


T.J. Carter
Senior Member of Techinal Staff - Hardware
DigiBoard, Inc.
UUNET Address : digibd!tjc