Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watmath!clyde!rutgers!ames!oliveb!pyramid!prls!mips!mash From: mash@mips.UUCP Newsgroups: comp.arch Subject: Re: Interrupt vectors. Message-ID: <440@winchester.UUCP> Date: Fri, 5-Jun-87 23:55:54 EDT Article-I.D.: winchest.440 Posted: Fri Jun 5 23:55:54 1987 Date-Received: Thu, 11-Jun-87 04:12:09 EDT References: <7408@boring.cwi.nl> <438@winchester.UUCP> <20461@sun.uucp> Reply-To: mash@winchester.UUCP (John Mashey) Organization: MIPS Computer Systems, Sunnyvale, CA Lines: 39 In article <20461@sun.uucp> guy%gorodish@Sun.COM (Guy Harris) writes: (regarding MIPS R2000) >The diagram in "Operating System Support on a RISC" shows both the >Status and Cause registers. The Cause register includes a 6-bit >ExtInt field, which I presume is a bitset indicating which of the 6 >external interrupts are pending. To what do these 6 interrupts >correspond? Do they correspond to classes of devices? I presume >you are not limited to 6 different devices attached to a system >containing an R2000, so you would "double up" on external interrupts >as necessary. > >If so, how are the devices distinguished? Is this done with polled >interrupts, or is some code provided in one of the other special >registers? 1) Thank goodness for people who actually read the literature! 2) The 6 bits correspond to whatever they're hooked to on the board. 3) On MIPS cpu boards, the 6 bits happen to be: Bus Error timeout profiling clock coprocessor interrupt scheduling clock onboard uarts vectored interrupts from VME 4) Some additional registers on the board record the VME interrupt info, so you can just go there and look, then take the appropriate vector. Nones of this is particularly different from anything else, i.e., the distinguishing info to identify an interrupt has to come from somewhere, and you can either do it in hardware, microcode, or software, or some combination, with RISCs confusing the issue a little, since the software is more like microcode. -- -john mashey DISCLAIMER: UUCP: {decvax,ucbvax,ihnp4}!decwrl!mips!mash, DDD: 408-720-1700, x253 USPS: MIPS Computer Systems, 930 E. Arques, Sunnyvale, CA 94086