;
;	File:		SonyWrite.a
;
;	Contains:	This file contains the disk driver routine used to write
;				data mark information on twiggy diskettes. This routine nibblizes
;				and computes the checksum on the fly, so it may be used for
;				one-to-one writing.
;
;	Written by:	Larry Kenyon
;
;	Copyright:	© 1982-1990, 1992 by Apple Computer, Inc., all rights reserved.
;
;	Change History (most recent first):
;
;	   <SM9>	 1/10/93	RC		Added Nops for Smurf
;	   <SM8>	12/14/92	RC		Restore to before PDM D2 Build with Horror Roll-in
;	   <SM5>	 12/7/92	rab		Roll in Horror changes. Comments followÉ
;		 <4>	11/14/91	SWC		Shortened the WrData patches for SWIM2 to save patch space.
;									Converted the SCC polling code to a macro to make it easier to
;									overpatch.
;		 <2>	10/18/91	CMP		Overpatched to support SWIM2.
;	   <SM4>	10/18/92	CCH		Added nop's for systems with non-serial writes to IO space.
;		 <5>	 7/14/92	CSS		Fixed the comment below so an exact version of this
;									file could be copied into SuperMario.
;		 <4>	 4/27/92	JSM		Get rid of conditionals: supportsMFM and forROM are always true.
;									This file now has no conditionals.
;		 <3>	 9/21/90	BG		Removed <2>. 040s are behaving more reliably now.
;		 <2>	 6/18/90	CCH		Added NOPs for flaky 68040's.
;	   <2.4>	 5/23/89	GGD		No changes to this file, entire Sony Driver is checked out and
;									in as a group.
;	   <2.3>	 4/29/89	GGD		No changes to this file, entire Sony Driver is checked out and
;									in as a group.
;	   <2.2>	 4/10/89	gmr		No changes to this file, entire Sony Driver is checked out and
;									in as a group.
;	   <2.1>	 2/21/89	GGD		No changes to this file, entire Sony Driver is checked out and
;									in as a group.
;	   <2.0>	12/15/88	GGD		No changes to this file, entire Sony Driver is checked out and
;									in as a group.
;	   <1.1>	11/11/88	CCH		Fixed Header.
;	   <1.0>	 11/9/88	CCH		Adding to EASE.
;	   <1.9>	 9/29/88	GGD		No changes to this file, entire Sony Driver is checked out and
;									in as a group.
;	   <1.8>	 9/19/88	GGD		No changes to this file, entire Sony Driver is checked out and
;									in as a group.
;	   <1.7>	 8/16/88	GGD		No changes to this file, entire Sony Driver is checked out and
;									in as a group.
;	   <1.6>	 7/15/88	GGD		No changes to this file, entire Sony Driver is checked out and
;									in as a group.
;	   <1.5>	 6/15/88	GGD		No changes to this file, entire Sony Driver is checked out and
;									in as a group.
;	   <1.4>	 5/25/88	GGD		No changes to this file, entire Sony Driver is checked out and
;									in as a group.
;	   <1.3>	 5/24/88	GGD		No changes to this file, entire Sony Driver is checked out and
;									in as a group.
;	   <1.2>	  5/3/88	GGD		No changes, entire sony driver checked out and in as a group.
;	   <1.1>	 4/18/88	GGD		Merged in MFM support <C437> by Steve Christensen
;	   <1.0>	 2/12/88	BBM		Adding file for the first time into EASEÉ
;	  <C437>	11/21/86	SWC		Patched WrData to jump to its MFM counterpart if we're running
;									in MFM mode.
;	  <A351>	 11/5/86	TJ		Text cleanup
;				 1/15/85	JTC		convert to MDS.
;				 8/15/83	LAK		A2 now passed in as parameter.
;				 7/21/83	LAK		No longer fill in Time (in TagData): done in SonyRWT.
;				 4/18/83	LAK		Rewrote to incorporate SCC channel A polling scheme.
;				11/18/82	LAK		Clear D0, D1 at start
;				 11/1/82	LAK		Added full handshaking for inclusion in ROM, 512-dot version.
;

			title 'File: SonyWrite.a'
;_______________________________________________________________________
;
; Routines: WrData
; Larry Kenyon	20/July/82
;
; Arguments:	  A0.L (input)	-- ptr to 512-byte data buffer
;		  A2.L (input)	-- ptr to data mark table.
;		  A4.L (input)	-- DiskQ6L pointer
;		  A5.L (input)	-- ptr to 6522 A-reg (has head sel, wait/req)
;		  A6.L (input)	-- ptr to  SCC channel A data register
;		  TagData (in)	-- sector # + 12 bytes of tag data to write
;		  D0.W (output) --
;			0 = no error
;			  -9 = write underrun detected
;		  A4-A6 are preserved
;		  all other registers are trashed
; Function: This file contains the disk driver routine used to write
;		data mark information on twiggy diskettes. This routine nibblizes
;		and computes the checksum on the fly, so it may be used for
;		one-to-one writing.
;
;		Since timing is tight coming into this routine, the disk
;		write-protect sense line should be checked by the read/write
;		track logic.
;
;
; Modification History:
;
; 01 Nov 82		LAK	Added full handshaking for inclusion in ROM, 512-dot version.
; 18 Nov 82		LAK	Clear D0, D1 at start
; 18 Apr 83		LAK	Rewrote to incorporate SCC channel A polling scheme.
; 21 Jul 83		LAK	No longer fill in Time (in TagData): done in SonyRWT.
; 15 Aug 83		LAK	A2 now passed in as parameter.
;
; 15 Jan 85		JTC	convert to MDS.
;_______________________________________________________________________
; A30230oct86	TJ	Removed absolute IWM addresses.
; A351 05Nov86	TJ	Text cleanup
;_______________________________________________________________________
;<C437/21nov86>	SWC	Patched WrData to jump to its MFM counterpart
;					if we're running in MFM mode.
;_______________________________________________________________________


			BLANKS	ON
			STRING	ASIS

HdrSize 	EQU 	8

MarkTbl		DC.B	$FF,$3F,$CF,$F3,$FC,$FF ; self-sync pattern
			DC.B	$D5,$AA 			; actual header ($AD written separately)

WrData
			BSR		GetDrv1				;Get the drive offset				<C437/21nov86>
			TST.B	mfmDisk(A1,D1)		;Are we in MFM mode?				<C437/21nov86>
			BMI		mWrData				;-> yes, do the MFM version			<C437/21nov86>

			LEA 	MarkTbl,A2			;
			MOVE.L	JWrData,-(SP)
			RTS

jtWrData	MOVE.L	(SP)+,DskRtnAdr 	; save	return address here

			LEA 	TagData+1,A1		; data first comes from TagData
			MOVE.L	#$2010009,D4		; adjusted byte write counts for 2 buffers
			MOVEQ	#0,D2				; clear high byte for indexing
			MOVEQ	#0,D3				;  D3 also: note D0,D1 cleared later

;_______________________________________________________________________
;
;	D7 = CkSumC 				A7 = stack (where poll data is pushed)
;	D6 = CkSumB 				A6 = ptr to SCC chan A data reg
;	D5 = CkSumA 				A5 = ptr to 6522 A-reg
;	D4 = loop counts			A4 = ptr to Q6L
;	D3 = A7A6B7B6C7C6 nibble	A3 = ptr to Q6H
;	D2 = C5C4C3C2C1C0 nibble	A2 = ptr to nibble, mark tables
;	D1 = B5B4B3B2B1B0 nibble	A1 = ptr to data buffer
;	D0 = A5A4A3A2A1A0 nibble	A0 = ptr to user buffer (to A1 after 12)
;
;_______________________________________________________________________

; first we write some self-sync bytes, data marks, and sector number

			MOVEQ	#0,D5				; zero the initial checksums
			MOVEQ	#0,D6				;
			MOVEQ	#0,D7				;
			MOVEQ	#HdrSize-2,D0		; write 1 byte on each side of loop
			MOVEA.L	SonyVars,A3			;									<SM5> begin
			TST.B	mfmMode(A3)			; are we in ISM mode?
			MOVEA.L	IWM,A3
			BPL.S	@NotSWIM2			; -> no, it's an IWM or SWIM
			LEA		rHandshake(A3),A4	; point to handshake
			LEA		wData(A3),A3		;  and write data registers for speed

			MOVE.B	#$F5,wPhase-wData(A3)	;select another drive addr to avoid
											; drive's index crosstalk problem
			TST.B	rError-wData(A3)		;Clear the error register
			MOVE.B	#$18,wZeroes-wData(A3)	;Clear the write and action bits
		if NonSerializedIO then
				nop							; force write to complete		<SM5>
		endif
			MOVE.B	#$10,wOnes-wData(A3)	;Set the write bit
		if NonSerializedIO then
				nop							; force write to complete		<SM5>
		endif
			MOVE.B	#$01,wOnes-wData(A3)	;Toggle clFIFO bit to clear out
		if NonSerializedIO then
				nop							; force write to complete		<SM5>
		endif
			MOVE.B	#$01,wZeroes-wData(A3)	; any data in the FIFO
		if NonSerializedIO then
				nop							; force write to complete		<SM5>
		endif
			TST.B	rError-wData(A3)		;Clear the error register again
			move.b	(A2)+,(A3)			; write first bit slip mark into FIFO

			MOVE.B	#$08,wOnes-wData(A3);Turn on the ACTION bit and go!
			BRA.W	WrHead				;
@NotSWIM2
			tst.b	Q6H(A3)				; first byte written is a bit wierd	<A302/30oct86>
			move.b	(A2)+,Q7H(A3)		; write first bit slip mark			<A302/30oct86>

			lea		Q6H(A3),A3			; set up Q6H pointer				<A302/30oct86>
										;									<SM5> end
WrHead		MOVE.B	(A2)+,D1			; grab nibble early
@1			TST.B	(A4)				; check write handshake
			BPL.S	@1					;
			MOVE.B	D1,(A3) 			; write out next header nibble
	if nonSerializedIO then
			nop							; force write to complete
	endif
			_PollSCC					; poll the SCC modem port			<H4><SM5>
@2			SUBQ.W	#1,D0				;
			BNE.S	WrHead				; leave D0=0, ex = 0

			MOVE.B	(A2)+,D1			; grab nibble early
			LEA 	Nibl,A2 			; let A2 point to nibble table
@3			TST.B	(A4)				; check write handshake
			BPL.S	@3					;
			MOVE.B	D1,(A3) 			; write out next header nibble
	if nonSerializedIO then
			nop							; force write to complete
	endif

			MOVEQ	#$0B,D1 			; last header byte not yet encoded ($AD)
			MOVE.B	(A1)+,D2			; get the sector number
			BRA.S	WrData2

WrDataSw	MOVE.L	A0,A1				; switch to user buffer

WrData1
			ADDX.B	D2,D7				; CSumC'' <- ByteC + CSumC' + ex
			EOR.B	D6,D2				; ByteC' <- ByteC XOR CSumB'
			MOVE.B	D2,D3				; D3 = [00][00][00][00][A7][A6][B7][B6]
										;	   [C7][C7][C5][C4][C3][C2][C1][C0]
			LSR.W	#6,D3				; D3 = [00][00][A7][A6][B7][B6][C7][C6]

@1			TST.B	(A4)				; check write handshake
			BPL.S	@1					;
			MOVE.B	0(A2,D3.W),(A3) 	; nibblize and write hi-bits out
	if nonSerializedIO then
			nop							; force write to complete
	endif

			SUBQ.W	#3,D4				; got 3 more bytes (wipes out ex bit!)
			MOVE.B	D7,D3				; D3 <- CSumC
			ADD.B	D7,D3				; ex <- CSumC[7]
			ROL.B	#1,D7				; CSumC' <- ROL (CSumC)
			AND.B	#$3F,D0 			; D0 = [00][00][A5][A4][A3][A2][A1][A0]

@2			_PollSCC					; poll the SCC modem port			<H4><SM5>

@3			TST.B	(A4)				; check write handshake
			BPL.S	@2					;
			MOVE.B	0(A2,D0.W),(A3) 	; write low ByteA out
	if nonSerializedIO then
			nop							; force write to complete
	endif

WrData2 	MOVE.B	(A1)+,D0			; read next ByteA
			ADDX.B	D0,D5				; CSumA' <- ByteA + CSumA + ex
			EOR.B	D7,D0				; ByteA' <- ByteA XOR CSumC'
			MOVE.B	D0,D3				; D3 = [A7][A6][A5][A4][A3][A2][A1][A0]
			ROL.W	#2,D3				;
			AND.B	#$3F,D1 			; D1 = [00][00][B5][B4][B3][B2][B1][B0]

@1			TST.B	(A4)				; check write handshake
			BPL.S	@1					;
			MOVE.B	0(A2,D1.W),(A3) 	; nibblize and write low ByteB out
	if nonSerializedIO then
			nop							; force write to complete
	endif

			MOVE.B	(A1)+,D1			; read next ByteB
			ADDX.B	D1,D6				; CSumB' <- ByteB + CSumB + ex
			EOR.B	D5,D1				; ByteB' <- ByteB XOR CSumA'
			MOVE.B	D1,D3				;
			ROL.W	#2,D3				;
			AND.B	#$3F,D2 			; D2 = [00][00][C5][C4][C3][C2][C1][C0]

			_PollSCC					; poll the SCC modem port			<H4><SM5>

@2			TST.B	(A4)				; check write handshake
			BPL.S	@2					;
			MOVE.B	0(A2,D2.W),(A3) 	; nibblize and write low ByteC out
	if nonSerializedIO then
			nop							; force write to complete
	endif

			MOVE.B	(A1)+,D2			; read next ByteC
			TST.W	D4					; reached end of buffer?
			BNE.S	WrData1 			;
			SWAP	D4
			BNE.S	WrDataSw			; br if we are switching to user buffer

; the last 2 data bytes are written out separately since they are odd . . .
; the missing third byte is just zero . . .

WrLast2 	CLR.B	D3					; D3 = [00][00][00][00][A7][A6][B7][B6]
										;	   [00][00][00][00][00][00][00][00]
			LSR.W	#6,D3				; D3 = [00][00][A7][A6][B7][B6][00][00]

@1			TST.B	(A4)				; check write handshake
			BPL.S	@1					;
			MOVE.B	0(A2,D3.W),(A3) 	; nibblize and write hi-bits out
	if nonSerializedIO then
			nop							; force write to complete
	endif

			MOVE.B	D5,D3				; start preparing 1st cksum byte
			ROL.W	#2,D3				;
			MOVE.B	D6,D3				;
			ROL.W	#2,D3				;
			AND.B	#$3F,D0 			; D0 = [00][00][A5][A4][A3][A2][A1][A0]

@2			TST.B	(A4)				; check write handshake
			BPL.S	@2					;
			MOVE.B	0(A2,D0.W),(A3) 	; write low ByteA out
	if nonSerializedIO then
			nop							; force write to complete
	endif

			AND.B	#$3F,D1 			; D1 = [00][00][B5][B4][B3][B2][B1][B0]

			_PollSCC					; poll the SCC modem port			<H4><SM5>

@3			TST.B	(A4)				; check write handshake
			BPL.S	@3					;
			MOVE.B	0(A2,D1.W),(A3) 	; nibblize and write low ByteB out
	if nonSerializedIO then
			nop							; force write to complete
	endif

; now we write out the three checksum bytes as 4 nibbles

WrCkSum 	MOVE.B	D7,D3				; D3 = [0][0][0][0][A7][A6][B7][B6]
										;	   [C7][C7][C5][C4][C3][C2][C1][C0]
			LSR.W	#6,D3				; D3 = [0][0][A7][A6][B7][B6][C7][C6]

@1			TST.B	(A4)				; check write handshake
			BPL.S	@1					;
			MOVE.B	0(A2,D3.W),(A3) 	; nibblize and write hi-bits out
	if nonSerializedIO then
			nop							; force write to complete
	endif

			AND.B	#$3F,D5 			; zero high 2 bits
@2			TST.B	(A4)				; check write handshake
			BPL.S	@2					;
			MOVE.B	0(A2,D5.W),(A3) 	; write CkSumA out
	if nonSerializedIO then
			nop							; force write to complete
	endif

			AND.B	#$3F,D6 			; zero high 2 bits
			_PollSCC					; poll the SCC modem port			<H4><SM5>

@3			TST.B	(A4)				; check write handshake
			BPL.S	@3					;
			MOVE.B	0(A2,D6.W),(A3) 	; write CkSumB out
	if nonSerializedIO then
			nop							; force write to complete
	endif

			AND.B	#$3F,D7 			; zero high 2 bits
@4			TST.B	(A4)				; check write handshake
			BPL.S	@4					;
			MOVE.B	0(A2,D7.W),(A3) 	; write CkSumC out
	if nonSerializedIO then
			nop							; force write to complete
	endif

; now, finally, write the two bit slip marks and FF byte

			MOVE.L	SonyVars,A2			;										<SM5> begin
			TST.B	mfmMode(A2)			;Are we in ISM mode?
			BPL.S	@NotSWIM2			; -> no, it's an IWM or SWIM
			LEA		@TrailMks2,A2
			MOVEQ	#6-1,D2				; 2 slip bytes plus four gap bytes

@WrSlipISM	MOVE.B	(A4),D1				;
			BPL.S	@WrSlipISM			;
			MOVE.B	(A2)+,(A3)			;
			_PollSCC					; poll the SCC modem port				<H5>
			DBRA	D2,@WrSlipISM		;

			MOVEQ	#0,D0				; assume no underrun
			BTST	#5,D1				; any errors?
			BEQ.S	@5					; branch if no underrun was detected
			MOVEQ	#WrUnderrun,D0		;
@5			MOVE.B	#$18,wZeroes-wData(A3)	;Clear the write and action bits
			BRA 	DskRtn				; share code (return via DskRtnAdr)

@TrailMks2	DC.B	$DE,$AA,$FF,$FF,$FF,$FF	;make sure enough gap bytes are written
											;to ensure that slip bytes get to disk
@NotSWIM2								;										<SM5> end
			LEA 	TrailMks,A2 		; set up for slip bytes
			MOVEQ	#3,D2				;

WrSlip		MOVE.B	(A4),D1
			BPL.S	WrSlip
			MOVE.B	(A2)+,(A3)
	if nonSerializedIO then
			nop							; force write to complete
	endif
			TST.B	(A5)				; SCC data available?
			BMI.S	@1					; br if not . . .
			MOVE.B	(A6),-(SP)			; push it on the stack
@1			DBRA	D2,WrSlip

			MOVEQ	#0,D0				; assume no underrun
			BTST	#6,D1				; any errors?
			BNE.S	@2					; branch if no underrun was detected
			MOVEQ	#WrUnderrun,D0
@2			tst.b	Q7L-Q6H(A3)			; get out of write mode after half		<A351/05nov86><A302/30oct86>
			BRA 	DskRtn				; share code (return via DskRtnAdr)

TrailMks	DC.B	$DE,$AA,$FF,$FF

; Normal Nibblizing Table: convert 6 bits into 8-bit code word.

Nibl

			DC.B	$96,$97,$9A,$9B,$9D,$9E,$9F,$A6
			DC.B	$A7,$AB,$AC,$AD,$AE,$AF,$B2,$B3
			DC.B	$B4,$B5,$B6,$B7,$B9,$BA,$BB,$BC
			DC.B	$BD,$BE,$BF,$CB,$CD,$CE,$CF,$D3
			DC.B	$D6,$D7,$D9,$DA,$DB,$DC,$DD,$DE
			DC.B	$DF,$E5,$E6,$E7,$E9,$EA,$EB,$EC
			DC.B	$ED,$EE,$EF,$F2,$F3,$F4,$F5,$F6
			DC.B	$F7,$F9,$FA,$FB,$FC,$FD,$FE,$FF