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From: gc0d+@andrew.cmu.edu (Glenn Cadoret)
Newsgroups: comp.sys.ibm-pc,comp.sys.ibm.pc
Subject: COM1 interrupts
Message-ID: <oYwKauu00WB3IJNEhE@andrew.cmu.edu>
Date: 22 Aug 89 14:56:58 GMT
Followup-To: comp.sys.ibm-pc
Organization: Physics, Carnegie Mellon, Pittsburgh, PA
Lines: 19

I have been trying to write a program for an IBM-AT which will catch
interrupts from COM1.  It is my understanding that three things must be done
to enable this type of interrupt:

1) Bit 7 of 0x3FB must be set low
2) Bits 0-3 of 0x3F9 must be set high
3) Bit 4 of 0x21 must be set low

I do all of these things, but I still don't see an interrupt.  Specifically,
I am interested in the interrupt which is generated when a character comes
into the port.
If anyone could suggest why program is not working, it would be greatly
appreciated.

Many thanks,
Glenn

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