Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!emory!ogicse!pdxgate!eecs!bairds
From: bairds@eecs.cs.pdx.edu (Shawn L. Baird)
Newsgroups: comp.sys.amiga.programmer
Subject: Direct hardware drive access
Message-ID: <2147@pdxgate.UUCP>
Date: 30 Mar 91 08:20:16 GMT
Sender: news@pdxgate.UUCP
Lines: 30

With the recent flamage/discussion I've revitalized some of my interest
in trying my hand at direct disk reading. I've included a small snippet
of code and will say that I can't even get the drive light to come on.
The code enters with Disable() having been called and all DMA turned
off (I'm not using any disk DMA for stepping out to track 0, so this
shouldn't be a problem should it?). The goal is to step the disk out to
track 0.

		; step to the outside of the disk in drive 0 (I wish)
		and.b	#$7f,ciaaprb		; select motor
		and.b	#$f7,ciaaprb		; select drive 0
diskready:	btst.b	#5,ciaapra		; check DSKRDY
		beq.s	diskready
		or.b	#$02,ciaaprb		; set step direction
checktrack0:	move.l	#3000,d0
		jsr	wait
		btst.b	#4,ciaapra		; check DSKTRACK0
		bne.s	disktrack0
		and.b	#$fe,ciaaprb		; step out
		or.b	#$01,ciaaprb
		bra.s	checktrack0
disktrack0:	or.b	#$88,ciaaprb		; unselect drive 0

The subroutine wait uses the cia timer to wait d0 microseconds and works
as far as I can tell. Didn't someone around here claim to have worked on,
or developed entirely, the trackdisk.device for 1.3 and 2.0? If so, help!

---
 Shawn L. Baird, bairds@eecs.ee.pdx.edu, Wraith on DikuMUD
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