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Newsgroups: comp.os.386bsd.questions Path: sserve!newshost.anu.edu.au!munnari.oz.au!yoyo.aarnet.edu.au!news.adelaide.edu.au!basser.cs.su.oz.au!news.cs.su.oz.au!metro!seagoon.newcastle.edu.au!wabbit.cc.uow.edu.au!dmssyd.syd.dms.CSIRO.AU!dmsperth.per.dms.CSIRO.AU!uniwa!harbinger.cc.monash.edu.au!yeshua.marcam.com!usc!elroy.jpl.nasa.gov!ames!ncar!csn!hellgate.utah.edu!lanl!nash!jxg From: jxg@purcell.lanl.gov (John M. Galbraith,(GRA)) Subject: Re: The Stray Interrupt Problem (7) under N Message-ID: <1994Feb7.173308.27261@newshost.lanl.gov> Sender: news@newshost.lanl.gov Reply-To: jxg@purcell.lanl.gov Organization: purcell LANL References: <2im84d$ahk@pdq.coe.montana.edu> Date: Mon, 7 Feb 1994 17:33:08 GMT Lines: 32 In article ahk@pdq.coe.montana.edu, nate@bsd.coe.montana.edu (Nate Williams) writes: > In article <2ilr1i$6fl@hrd769.brooks.af.mil>, > Dave Burgess <burgess@hrd769.brooks.af.mil> wrote: > >It this example, I would think that a much more likely culprit than random > >lpt interrupts would be that the cable in this case was bad/marginal. > > The interrupt 7's are caused by interrupts that are sent but not received. > > So, if the wd driver sends out an interrupt but some other driver (or itself) > blocks interrupts for too long a time then a stray interrupt is generrated. < stuff deleted > I was wondering if somebody in the know could examine this a bit more. I have been hacking on a MIDI driver and have apparently run into this, although I did not know what the problem was until reading this thread. Every once in a while the driver drops a character. (MIDI is serial, 31.25Kbaud) It turns out that I am getting stray interrupt 7's whenever this happens. Apparently, the interrupts for these missing characters are being ignored, and that is why the stray interrupt, and the missing character. I don't mask the interrupts at all, so I don't suspect that they are being blocked for too long. Not masking at all could be the problem too, I suppose. Does that mean that the interrupt routine is just plain too long, and the next character interrupts the currently running interrupt routine? What kind of timing problems might be possible, and how does one go about finding them? Also, before you say that there is a mpu driver in the sound driver code, I know that. I want to use the mpu as a coprocessor, not just a UART. john