tom@.berkeley.edu (09/16/88)
I have designed an interface to the MacII using all the APDA info that I can get. It all works great, but with one snag. I can't get the Mac to recognize an interrupt. I have been able to generate and recieve an interrupt from a debounced switch, but from this interface, no success. My suspicion is that the Mac needs a longer pulse, though I am up to 200 nsec. and that seems plenty long. Any ideas?
tom@jif.berkeley.edu (tom erbe) (09/16/88)
oops--- i forgot my signature tom erbe-technical director-center for contemporary music-mills college tom@jif.berkeley.edu
paul@unisoft.UUCP (n) (09/19/88)
In article <14327@agate.BERKELEY.EDU> tom@.berkeley.edu () writes: > > I have designed an interface to the MacII using all the APDA info >that I can get. It all works great, but with one snag. I can't get the >Mac to recognize an interrupt. I have been able to generate and recieve an >interrupt from a debounced switch, but from this interface, no success. My >suspicion is that the Mac needs a longer pulse, though I am up to 200 nsec. >and that seems plenty long. Any ideas? Bad news I'm afraid ... the answer is 'as long as is required' what you have to do is design hardware where the software cancels the interrupt. I do this on all my cards (actually I decode WRITES to my ROMs since noone uses these - writes to odd addresses cancel pending NuBus interrupts, writes to even addresses interrupt the onboard processor etc). Anyway put a latch for the interrupt that is set by the peripheral that is requesting it and cleared by some sort of bus traffic, the MacOS handler you write should generate the required traffic to clear it. What is happening for you at the moment is that the 68020 is probably taking the interrupt and polling all the possible sources for it, finding none it just returns to where it came from. Paul Campbell -- Paul Campbell, UniSoft Corp. 6121 Hollis, Emeryville, Ca E-mail: ..!{ucbvax,hoptoad}!unisoft!paul Nothing here represents the opinions of UniSoft or its employees (except me) "Nuclear war doesn't prove who's Right, just who's Left" (ABC news 10/13/87)