Alpha One’s Track loader

init:	move.w	$dff01c,oldintena

	move.w	$dff01e,oldintreq

	bset	#7,oldintena

	bset	#7,oldintreq

	move.w	#$7fff,$dff09a		; interrupts aus.

	move.w	#$7fff,$dff09c		; 

;****************************************************************
	lea	$dff000,a6

	lea	buffer(pc),a0

	lea	mfmbuffer,a2

	move.l	#5*$1600,d0

	move.l	#0,d1

	move.l	#$0,d2

	jsr	trackloader
;****************************************************************
	move.w	oldintena(pc),$dff09a

	move.w	oldintreq(pc),$dff09c

	moveq	#0,d0

	rts
oldintena:	dc.w	0

oldintreq:	dc.w	0

buffer:		blk.b	130000,0

mfmbuffer:	blk.w	6400,0
; ============================================================================
; HARDWARE-DISKLOADER (c) ALPHA ONE 2005.

; ***************************************

; IMPROVED TO READ FROM ODD BYTEPOSITIONS.

; PRO VERSION -> WITH TRACKCOUNTER.

; IN: A6=$DFF000

;     A2=MFMBUFFER.L

;     A0=BUFFER.L

;     D0=LENGTH.L

;     D1=TRACKNR.L

;     D2=BYTEOFFSET.L
TRACKLOADER:
		LEA	$BFD100,A4		; DRIVESELECT REGISTER

		LEA	$BFE001,A5		; DRIVESTATUS REGISTER

		LEA	CURRENTTRACK(PC),A3	; HOLDS THE ACTUAL TRACKPOS

		MOVEQ	#0,D7			; D7 = BYTECOUNTER

		ADD.L	D2,D0			; BYTES TO READ + BYTEOFFSET

		MOVE.L	D0,D3

		DIVS.W	#$1600,D3

		MOVE.B	D3,1(A3)
		MOVE.B	#$7D,(A4)		; SWITCH MOTOR DRIVE 0 ON

		NOP				; =======================

		NOP

		MOVE.B	#$75,(A4)

		BSR.W	DELAY

		BSR.W	DISKREADY
		CMP.B	#$FF,(A3)

		BNE.B	MOVETOCYLINDER

		MOVE.B	#0,(A3)

		BSET	#1,(A4)			; CHOSE DIRECTION TOWARDS 0

MOVETOZERO:	BTST	#4,(A5)			; HEAD ON CYLINDER 0?

		BEQ.B	MOVETOCYLINDER

		BSR.W	MOVEHEAD		; MOVE HEAD + DELAY

		BRA.B	MOVETOZERO	
MOVETOCYLINDER:	BSET	#2,(A4)			; CHOOSE HEAD HIGH

		BTST	#0,D1			; EVEN OR ODD TRACK?

		BEQ.B	HEADOK			; TRACK IS EVEN – ALRIGHT!

		BCLR	#2,(A4)			; CHOOSE HEAD LOW

HEADOK:		MOVEQ	#0,D3

		MOVEQ	#0,D5

		MOVE.B	D1,D3			; NEW TRACKNUM -> D3

		MOVE.B	(A3),D5			; CURRENT TRACK -> D5

		MOVE.B	D1,(A3)			; REPLACE CURRENT TRACK

		LSR.W	#1,D3			; GET CYLINDER NUM NEW TRACK

		LSR.W	#1,D5			; GET CYLINDER NUM CUR TRACK

		SUB.W	D3,D5

		BEQ.B	READTRACK

		BMI.B	OTHERDIRECTION

		BSET	#1,(A4)			; CHOOSE DIRECTION TOWARDS 0

		BRA.B	CHOSEN

OTHERDIRECTION:	BCLR	#1,(A4)			; CHOOSE DIRECTION OUTWARDS 0

		NEG.W	D5

CHOSEN:		BSR.W	MOVEHEAD

		SUBQ.B	#1,D5

		BNE.B	CHOSEN
READTRACK:	BSR.W	DISKREADY		; EINEN TRACK LESEN

		MOVE.W	#$8210,$96(A6)		; =================

		MOVE.W	#$7F00,$9E(A6)

		MOVE.W	#$8500,$9E(A6)

		MOVE.W	#$4489,$7E(A6)

		MOVE.W	#$4000,$24(A6)

		MOVE.L	A2,$20(A6)

		MOVE.W	#$9900,$24(A6)

		MOVE.W	#$9900,$24(A6)

		MOVE.W	#$2,$9C(A6)

TRACKREADY:	BTST	#1,$DFF01F

		BEQ.B	TRACKREADY

		MOVE.W	#$4000,$24(A6)
		MOVEQ	#0,D5			; DECODE TRACK

DECODE:		MOVE.L	A2,A1			; ============

		MOVE.L	#$55555555,D4

FINDSYNC:	CMP.W	#$4489,(A1)+

		BNE.B	FINDSYNC

		CMP.W	#$4489,(A1)

		BEQ.B	FINDSYNC

		MOVE.L	(A1),D3

		MOVE.L	4(A1),D1

		AND.L	D4,D3

		AND.L	D4,D1

		ASL.L	#1,D3

		OR.L	D1,D3

		ROR.L	#8,D3

		CMP.B	D5,D3

		BEQ.B	SECTORFOUND

		ADD.L	#1086,A1

		BRA.B	FINDSYNC

SECTORFOUND:	ADD.L	#56,A1

		MOVE.L	#(512/4)-1,D6

DECODESECTOR:	MOVE.L	512(A1),D1

		MOVE.L	(A1)+,D3

		AND.L	D4,D3

		AND.L	D4,D1

		ASL.L	#1,D3

		OR.L	D1,D3

		LEA	STORE(PC),A3

		MOVE.L	D3,(A3)
		MOVEQ	#4-1,D3

LOOP:		CMP.L	D7,D0

		BEQ.B	READREADY

		CMP.L	D7,D2

		BGT.B	BELOW

		MOVE.B	(A3),(A0)+

BELOW:		ADDQ.L	#1,A3

		ADDQ.L	#1,D7

		DBF	D3,LOOP
		DBF	D6,DECODESECTOR

		ADDQ.B	#1,D5

		CMP.B	#11,D5

		BNE.B	DECODE
TRACKDONE:	CMP.L	D7,D0			; TRACK DONE, GET ONTO NEXT.

		BEQ.B	READREADY		; ==========================

		BTST	#2,(A4)

		BEQ.B	ONTONEXT

		BCLR	#2,(A4)

		BSR.W	DELAY

		BRA.W	READTRACK

ONTONEXT:	BSET	#2,(A4)

		BSR.W	DELAY

		BCLR	#1,(A4)

		BSR.W	MOVEHEAD

		BRA.W	READTRACK
READREADY:	MOVE.B	#$FD,(A4)		; SWITCH MOTOR DRIVE 0 OFF

		NOP				; ========================

		NOP

		MOVE.B	#$E7,(A4)

		LEA	CURRENTTRACK(PC),A3

		MOVE.B	1(A3),D0

		ADD.B	D0,(A3)

		RTS
DELAY:		CLR.B	$300(A4)		; DELAY ROUTINE

		MOVE.B	#$19,$400(A4)		; =============

		MOVE.B	#$1,$D00(A4)

WAIT:		BTST	#0,$C00(A4)

		BEQ.B	WAIT

		BCLR	#0,$D00(A4)

		RTS
DISKREADY:	BTST	#5,(A5)			; WAIT FOR DISK-READY

		BNE.B	DISKREADY		; ===================

		RTS
MOVEHEAD:	BCLR	#0,(A4)

		BSR.W	DELAY

		BSET	#0,(A4)

		BSR.W	DELAY

		RTS		
CURRENTTRACK:	DC.B	$FF,0

STORE:		DC.L	0
TRACKLOADERENDE:
; ============================================================================

Publication author

offline 4 hours

mus@shi9

0

Comments: 1166Publics: 2810Registration: 06-03-2017