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Newsgroups: comp.os.386bsd.questions Path: sserve!newshost.anu.edu.au!munnari.oz.au!bunyip.cc.uq.oz.au!un!pc012 From: pc012@un.seqeb.gov.au ( PAT COLLINS) Subject: Timer ISR Message-ID: <CKMzoo.2rz@un.seqeb.gov.au> Organization: SEQEB X-Newsreader: TIN [version 1.2 PL2] Date: Thu, 3 Feb 1994 07:05:11 GMT Lines: 20 I would like to hack the FreeBSD system to read a digital io card. This is basically just a card with 4 8255 PIA's on it. The PIA's are connected to electricity meters which output a pulse for a unit of energy consumed. To be able to succesfully detect thiese pulses I need to read the PIA every 10 mS or so. Is it possible to hack the kernels ISR that services the 8253 timer 0 interrupt (int 8) and how or where could the data read and stored such that it can be accessed by a user process. I have written this type of system running under DOS OK but I would like to run under UNIX for a variety of reasons. Could anyone tell me where in the source tree I need to look to start on this project or give me any other usefull advice. Can FreeBSD be used as the basis of an industrial control system ? Thanks. Patrick Collins pc012@seqeb.gov.au