Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!att!cbnewsc!normt
From: normt@cbnewsc.ATT.COM (Norman R Tiedemann)
Newsgroups: comp.sys.m68k
Subject: Re: autovector on the '010
Message-ID: <15005@cbnewsc.ATT.COM>
Date: 10 Apr 90 21:43:51 GMT
References: <7821@quick.COM>
Reply-To: normt@cbnewsc.ATT.COM (Norman R Tiedemann)
Organization: AT&T Bell Laboratories
Lines: 40

In article <1990Apr07.090036.26347@csuchico.edu>, garlick@csuchico.edu (Jim Garlick) writes:
>> In my 68010 manual, I'm having a hard time finding where it says
>> how to use interrupt autovectoring.  On the 030 and 040, you pull
>> the AVEC* line, right?  What do you do on the 010 and 020?  I'd 
>> like to avoid handling an interrupt acknowledge cycle at all, 
>> if possible.
>
>Can't avoid it.  The best way I've found to handle this problem is
>to make sure that the last 7 words of the physical address space
>are in RAM or ROM and then put the autovector numbers there.  If you
>don't mind a bit of hardware, the a single '244 or '245 on the
>low byte will do (selected by fc=111).

This is not correct! It is easy to do on the 68000 or 68010. I have designed
a couple of processor boards with autovectoring using 68010. It is described
in the section dealing with M6800 interfacing (6.3 in my hardware manual)

The description is: During an interrupt acknowledge cycle while the 
processor is fetching the vector, if VPA is asserted (0) the MC68010 will
assert VMA and complete a normal M6800 read cycle as shown in Figure 6-4. The
processor will then use an internally generated vector that is a function 
of the interrupt being serviced. This process is known as autovectoring. 
The seven autovectors are vector numbers 25 through 31 (decimal).

Basically what this means is you NAND together FC0, FC1, FC2, and AS(inverted),
and feed this output into the VPA input on the processor.
So only when all three function control lines are high (CPU space) and the
address strobe is low (valid cycle) will the VPA signal be activated, this is
the code for the 68010 (and 68000) to do autovectoring.

It is completely there, but I agree that the description in the manual
is not in an obvious place at all. Hope this helps.

	Norm Tiedemann		AT&T Bell Labs IH 2G-419
	att!ihlpy!normt		2000 Naperville Rd.
	normt@ihlpy.att.com	Naperville, IL	60566
-- 
	Norm Tiedemann		AT&T Bell Labs IH 2G-419
	att!ihlpy!normt		2000 Naperville Rd.
	normt@ihlpy.att.com	Naperville, IL	60566