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From: grr@cbmvax.cbm.UUCP (George Robbins)
Newsgroups: comp.sys.amiga
Subject: Re: Audio Interrupt
Message-ID: <1008@cbmvax.cbmvax.cbm.UUCP>
Date: Wed, 19-Nov-86 02:15:05 EST
Article-I.D.: cbmvax.1008
Posted: Wed Nov 19 02:15:05 1986
Date-Received: Wed, 19-Nov-86 05:56:48 EST
References: <937@zen.BERKELEY.EDU> <1188@tekcrl.UUCP>
Reply-To: grr@cbmvax.UUCP (George Robbins)
Organization: Commodore Technology, West Chester, PA
Lines: 23
Keywords: 68000 interrupt

In article <1188@tekcrl.UUCP> terryl@tekcrl.UUCP writes:
>In article <937@zen.BERKELEY.EDU> c55-hd@buddy.Berkeley.EDU (Bob Johnsen) writes:
> >Where does one put the address for a level 4 audio interrupt handler?
> >I thought it was $74, but there seems to be a problem.
> >I set intena bits 15 14 and 7, start the dma, get the tone....but
> >the amiga immediately crashed.
>
>     Not knowing anything about the Amiga, but knowing quite a bit about the
>various flavors of 68xxx processors, the level 4 autovector is at 70 (hex, that
>is; I'm assuming $74 is hex 74).

Well, actually the Amiga doesn't auto-vector.  Because of the way the logic
is implemented, it fetches the interrupt identifier from "ROM" at address
FFFFFX where X is the interrupt level shifted left a bit.  In release 1.2,
the interrupt identifiers thusly fetched correspond to the autovector
locations, which from a software point of view is identical to autovector.
I've heard that under some previous releases, all the identifiers were the
same, but don't know if this is/was really the case.

-- 
George Robbins - now working for,	uucp: {ihnp4|seismo|rutgers}!cbmvax!grr
but no way officially representing	arpa: cbmvax!grr@seismo.css.GOV
Commodore, Engineering Department	fone: 215-431-9255 (only by moonlite)