Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!julius.cs.uiuc.edu!apple!vsi1!octopus!stever From: stever@Octopus.COM (Steve Resnick ) Newsgroups: comp.os.msdos.programmer Subject: Re: COM1 COM2 interrupt numbers? Message-ID: <1990Sep26.184334.13477@Octopus.COM> Date: 26 Sep 90 18:43:34 GMT References: Reply-To: stever@octopus.UUCP (Steve Resnick ) Organization: Octopus Enterprises, Cupertino CA Lines: 37 In article jc58+@andrew.cmu.edu (Johnny J. Chin) writes: >First of all ... the hardware interrupt for the serial ports are 3 or 4, by >default. > >COM1 - IRQ4 (hardware interrupt request #4) >COM2 - IRQ3 > >As for some other common ones: > >INT 0 - NMI (non-maskable interrupt) - usually due to memory parity error >INT 1 - reserved >INT 2 - used by many EGA/VGA cards (usually available on 8088) > cascading interrupt on 286/386/486 machines >INT 3 - COM2: >INT 4 - COM1: >INT 5 - Hard Disk Controller on 8088 (available for LPT2: on 286/386/486) >INT 6 - Floppy Controller >INT 7 - LPT1: > >INT 14 - cascaded off INT 2 - Hard Disk Controller on 286/386/486. > > >I hope this information helps ... These are IRQ's, not INTS - ie, when COM1 needs service it DOES NOT issue an int 3, it issues an INT 0BH. Note that IRQ interrupts start at int 08H the timer vector. Based on this I think that INT 0 is not an IRQ but an INT line on the CPU, otherwise, the timer would be vectored to NMI (which it isn't) Steve -- ---------------------------------------------------------------------------- steve.resnick@f105.n143.z1.FIDONET.ORG - or - apple!camphq!105!steve.resnick Flames, grammar errors, spelling errrors >/dev/nul ----------------------------------------------------------------------------