Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!pws1!srw
From: srw%pws1@Sun.COM (Scott Wiesner)
Newsgroups: comp.os.minix
Subject: Re: PS/2 level-triggered interrupts
Message-ID: <85692@sun.uucp>
Date: 17 Jan 89 19:18:16 GMT
References: <1907@ast.cs.vu.nl>
Sender: news@sun.uucp
Lines: 14

From article <1907@ast.cs.vu.nl>, by ast@cs.vu.nl (Andy Tanenbaum):
> I suspect what they are trying to say is that if the EOI is issued when the
> level-triggered interrupt is still asserted, you get another interrupt.
> Thus, there is no way to have the 8259A fix the problem.  The floppy disk
> controller must be given some sort of command to tell it to negate the
> interrupt.  Furthermore, every other device (clock, hard disk, network, 
> etc) that can generate interrupts has the same problem.

Yes!  That's what my earlier article was trying to say.  For the floppy, 
the command happens to be a sense interrupt status command, which has
a value of 8.  On some devices (like the serial port), just reading the
status (which you do anyway) causes the interrupt to reset.  

Scott