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From: hauerwas@gymble.umd.edu@hvrunix.UUCP
Newsgroups: mod.computers.vax
Subject: Submission for mod-computers-vax
Message-ID: <8702271702.AA15003@hvrunix.UUCP>
Date: Fri, 27-Feb-87 17:02:46 EST
Article-I.D.: hvrunix.8702271702.AA15003
Posted: Fri Feb 27 17:02:46 1987
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Path: hvrunix!hauerwas
From: hauerwas@hvrunix.UUCP (Adam Hauerwas)
Newsgroups: mod.computers.vax,comp.sys.att,comp.terminals
Subject: Driver for the COM port on an AT&T 6300+
Message-ID: <288@hvrunix.UUCP>
Date: 27 Feb 87 22:02:45 GMT
Organization: Haverford College, Haverford, PA
Lines: 25


     The following is a message from the Vax System Manager here at
Haverford.  I'm posting it to the groups I think might know how to deal
with it.  Please respond through E-Mail to either "hauerwas!hvrunix" or
"A_HAUERWAS @ HVRFORD.BITNET"  Thanks in advance.

                               *     *     *

     I am trying to write a driver for the COM port on an AT&T 6300+ with
the OS Merge operating system.  I am able to address the chip ports and can
send single characters out on the line (a line monitor has verified this).
However, I am unable to receive interrupts.  The chip is posting the
interrupts but somehow they are getting masked out. 
	
     I am running on interrupt 4 (the default driver has been removed).  
When I read the 8259 (PIC) enable register I get a value of 13 which means
that only interrupts 0, 2, and 3 are enabled.  I enable interrupt 4 and read
the register which gives a value of 29 (as it should).  However, on the very
next instruction I read the register again and the value has returned to 13.
Any ideas?

							Bob Kostes
							Systems Manager
							Haverford College
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