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From: apfiffer@admin.ogi.edu (Andy Pfiffer)
Newsgroups: comp.unix.sysv386
Subject: 8254 timer usage under Sys V/386 R3.2?
Message-ID: <16808@ogicse.ogi.edu>
Date: 1 Feb 91 06:02:41 GMT
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I'd like to be able to program and poll one of the timers on the 8254
Programmable Interval Timer under a vanilla System V/386 R3.2.  I have
no difficulty accessing the ports, but I'm not certain how UNIX uses them.

There are three 1.19 MHz timers on the chip.  My guesses:

	Timer	Function
	    0	100Hz clock interrupt
	    1	DRAM refresh (about 66 KHz)
	    2	beep & buzz

Are these correct?

Thanks.

--
Andy Pfiffer	(503) 645-1886				apfiffer@admin.ogi.edu
Formerly w/ Cogent Research, Formerly w/ Topologix, Formerly w/ Theory Center.
"To determine where to resume execution upon leaving the trap handler, examine
the instruction at address fir - 4.