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Path: utzoo!utgpu!water!watnot!watmath!clyde!bellcore!faline!ulysses!gatech!seismo!rutgers!mit-eddie!uw-beaver!tektronix!tekcrl!vice!tekfdi!bobb
From: bobb@tekfdi.UUCP
Newsgroups: comp.sys.amiga
Subject: Re: HNeed help with MIDI program
Message-ID: <812@tekfdi.TEK.COM>
Date: Wed, 4-Mar-87 12:38:50 EST
Article-I.D.: tekfdi.812
Posted: Wed Mar  4 12:38:50 1987
Date-Received: Sat, 7-Mar-87 00:04:57 EST
References: <432@unisec.USI.COM>
Reply-To: bobb@tekfdi.UUCP (Robert Bales)
Distribution: comp
Organization: Tektronix, Inc., Beaverton, OR.
Lines: 41
Keywords: interrupt handler

[This article dealt with trying to make an interrupt handler work in a public-
domain MIDI program.]

After 1/2 week, I've succeeded (I think) in getting an interrupt handler to
work. My application was somewhat different, so I don't know if all this
applies, but here goes. . . .

The "move d1,a4" sounds like it comes from the Aztec manual, which is wrong.
The RKM indicates the data area pointer is in a4, so the instruction is
"move.l a1,a4." This is the 2nd thing to be done, however. The first is to
save the existing registers on the stack, since, at least for Aztec, a4 must be
preserved. If memory serves me right, the instruction to do this is
"movem.l d0-d7/a0-a7, -(a7)." Actually, probably only the registers needed by 
the compiler must be saved. So my handler looks like:

handleInt()
{
#asm
    MOVEM.L D0-D7/A0-A7, -(A7)
    MOVE.L A1,A4
#endasm
[C interrupt code]
#asm
    MOVEM.L (A7)+, D0-D7/A0-A7
    [Set interrupt return code]
#endasm
}

Like I said, the assembler syntax may not be exact. Setting the return code
depends on exactly what you are doing, as discussed in the RKM. I set up the
date field pointer in the Interrupt structure as discussed in the Aztec manual
(probably different for Lattice).

Anyway, I'm using one handler in the vertical blank chain to count frames, and
then call another handler via Cause() every second. So far, the guru has stayed
away. . . .

   Bob Bales
   Tektronix, Inc.

I help Tektronix make their instruments. They don't help me make my opinions.