PAGE

;	Read a CP/M 128 byte sector.
;
;	EXIT	A = 0, successful read operation.
;		A = 1, unsucessful read operation.
;		Z bit = 1, successful read operation.
;		Z bit = 0, unsuccessful read operation.

READ:	proc
	CALL	CHKBKD		;Check for blocked drive
	LD	AL,#F.RDAT
	JNC READ1	! JMP FINAL	;If unBlocked transfer
READ1:
	XOR	AL,AL		;Set flag to force a read
	STO	AL,UNACNT	;Clear sector counter
	CALL	FILL		;Fill buffer with data
	LD	ES,DMASEG	;Destination segmentation register
	LD	DI,DMAADR
	LD	DS,BUFSEG	;Set source segmentation register
	POP	SI
	LD	CX,#128/2	;Move 128 bytes
	CLD			;Clear direction
	REP			;Repeat until CX = 0
	MOVS			;Move the data to user's memory
	POP	DI		;Restore save registers
	POP	SI
	POP	DS
	POP	ES
	LD	AL,ERFLAG
	CMP	AL,#0
	JE	READ2		;If no error
	LD	AL,#0
	STO	AL,HSTACT	;Clear host active
	OR	AL,#001h	;Set error flag
READ2:	RET
	SPACE	4,20
;	Write the selected 128 byte CP/M sector.
;
;	ENTRY	C = 0, write to a previously allocated block.
;		C = 1, write to the directory.
;		C = 2, write to the first sector of unallocated
;		data block.
;
;	EXIT	A = 0, write was successful.
;		A = 1, write was unsucessful.
;		Z bit = 1, write was successful.
;		Z bit = 0, write was unsucessful.

WRITE:	proc
.ldr	IF	@LDR
	RET
.ldr	else

	CALL	CHKBKD		;Check for blocked drive
	JNC	WRIT1		;If blocked transfer
	LD	AL,#F.WRT	;Write to single density floppy
	JMP	FINAL

WRIT1:	STO	CL,WRTYPE
	CMP	CL,#WRUAL
	JNE	WRIT3		;If write to allocated

	LD	AL,SEKTYP
	CMP	AL,#MAXFTP
	LD	AL,#2048/128
	JLE	WRIT2		;If floppy disk
	LD	AL,#4096/128

WRIT2:	STO	AL,UNACNT
	LD	AX,SEKTRK
	STO	AX,UNATRK	;UNATRK = SEKTRK
	LD	AL,LOGSEC
	INC	AL
	JMP	WRIT4

WRIT3:	LD	AL,UNACNT
	CMP	AL,#0
	JE	WRIT5		;If no unallocated records
	DEC	AL
	STO	AL,UNACNT
	LD	BL,SEKTYP
	ROR	BL
	LD	BH,#0
	ADD	BX,#LSITT-1
	LD	AL,UNASEC	;Increment logical sector
	INC	AL
	CMP	AL,[BX]		;Last sector in track table
	JNE	WRIT4		;If not end of track
	LD	AX,UNATRK
	INC	AX
	STO	AX,UNATRK
	LD	AL,#0

WRIT4:	STO	AL,UNASEC
	LD	AL,#0FFh

WRIT5:	CALL	FILL
	LD	ES,BUFSEG	;Destination segmentation register
	POP	DI
	LD	SI,DMAADR
	LD	DS,DMASEG	;Source segmentation
	LD	CX,#128/2	;Move 128 bytes
	CLD			;Clear direction
	REP			;Repeat until CX = 0
	MOVS			;Move the data to user's memory
	POP	DI		;Restore save registers
	POP	SI
	POP	DS
	POP	ES
	LD	AL,#1
	STO	AL,HSTWRT	;HSTWRT = 1
	LD	AL,ERFLAG
	CMP	AL,#0
	JNE	WRIT7		;If any errors occurred

	LD	AL,WRTYPE	;write type
	CMP	AL,#WRDIR	;to directory?
	JNE	WRIT6		;If not directory write
	CALL	FLUSH		;Force write of directory
WRIT6:	LD	AL,ERFLAG
	CMP	AL,#0
WRIT7:	RET

LSITT:	DB	2*26		;Double 256 byte
	DB	4*15		;Double 512 byte
	DB	8*8		;Double 1024 byte
	if	hard
	if	gbc20
	db	8*11
	endif
	if	gbc10
	db	8*11
	endif
	if	gbc26
	db	8*18
	endif
	endif
.ldr	endif
	PAGE
;	TREAD - Determine floppy disk type.
;
;	ENTRY	C = Selected drive.
;
;	Exit	Zbit set = no error
;		A = disk type (0-3)

TREAD:	MOV	AL,CL
	ADD	AL,#'A'
	STO	AL,NRDYM2	;Set drive into message
	CALL	SPECIFY		;Set disk parameters
	LD	CX,#240		;Delay for head selects
	CALL	DELAY
	LD	AL,SEKDSK	;Move drive to command buffer
	STO	AL,ACTDSK	;Set into ACTDSK
	LD	BX,#DSTS
	LD	CX,#DSTSL
	CALL	EXECP		;Perform command
	LD	CX,#1
	CALL	GCMPS		;Get the one status byte
	TEST	AL,#020h	;Mask ready bit
	JNZ	TRD2		;If drive is ready
	LD	BX,#NRDYM1
	CALL	PRINT
	OR	AL,#0FFh	;Clear zero flag
TRD1:	RET

TRD2:	AND	AL,#008h	;Mask TS bit
	ROR	AL
	ROR	AL
	ROR	AL
	STO	AL,SEKTYP	;Save sided flag
	LD	BX,#RECAL	;Do a test seek
	LD	CX,#LRECAL
	CALL	MOVETO		;Process command
	JNZ	TRD1		;If error

	LD	AL,#2		;Seek to track two
	CALL	DOSEEK		;Do seek
	JNZ	TRD1		;If error

	LD	AL,#F.DRID
TRD3:	STO	AL,DRID
	LD	BX,#DRID
	LD	CX,#DRIDL
	LD	DX,#7
	CALL	EXECX		;Process command
	JZ	TRD4		;If read valid
	LD	AL,DRID
	XOR	AL,#040h	;Compliment MFM bit
	TEST	AL,#040h
	JNZ	TRD3		;If MFM not tried
	OR	AL,#0FFh
	RET

TRD4:	LD	AL,TEMPBF+6	;Get number of bytes
	SHL	AL
	OR	AL,SEKTYP	;Combine N with sided flag
	CMP	AL,AL		;Set zero flag
	RET

DSTS:	DB	F.DSTS,0
DSTSL:	EQU	*-DSTS

RECAL:	DB	F.RECA,0
LRECAL:	EQU	*-RECAL

DRID:	DB	F.DRID,0
DRIDL:	EQU	*-DRID

NRDYM1:	DB	CR,LF,'Drive '
NRDYM2:	DB	'x'
	DB	' not ready.',0
	PAGE
;	FILL - fill host buffer with approprite host sector.
;
;	ENTRY	A = 0, Read required if not in buffer.
;		0therwise read not required.
;
;	EXIT	On exit the stack will contain the following
;		values:
;	POP     x         ;x = host record address.
;	POP     y		;y = caller's buffer address.

FILL:	STO	AL,RDFLAG	;Save read flag
	LD	AL,SEKTYP	;Get disk type
	CMP	AL,#MAXFTP
	JLE	FILL1		;If floppy disk
	LD	AL,#6		;2*((LOG BASE 2 (1024)-7) (FOR HARD DISKS)

FILL1:	ROR	AL		;divide by 2
	AND	AL,#3h
	MOV	CL,AL		;log base 2 (sector size) - 7
	LD	AL,SEKSEC	;Get sector number
	LD	AH,#0
	ROR	AX,CL		;Get true sector number
	STO	AL,SEKSEC
	ADD	CL,#7		;log base 2 (sector size)
	LD	AL,#0
	ROL	AX,CL
	ADD	AX,#HSTBUF	;Sector in buffer
	POP	CX		;Get return address
	PUSH	ES		;Save destroyed registers
	PUSH	DS
	PUSH	SI
	PUSH	DI
	PUSH	AX
	PUSH	CX		;Set return address

	LD	BX,#HSTACT	;host active flag
	LD	AL,[BX]
	STOB	#1,[BX]		;always becomes 1
	CMP	AL,#0
	JE	FILL4		;If host buffer inactive
	LD	DI,#HSTSEC
	LD	SI,#SEKSEC
	LD	CX,#SEKTYP-SEKSEC+1
	MOV	AX,CS
	MOV	ES,AX
	CLD
	REPE			;REPeat while Equal
	CMPSB
	JZ	FILL5		;If all bytes same
	CALL	FLUSH		;Flush host buffer

FILL4:	LD	AX,SEKDSK	;Move disk and type
	STO	AX,HSTDSK
	STO	AX,ACTDSK
	LD	AX,SEKTRK
	STO	AX,HSTTRK
	STO	AX,ACTTRK
	LD	AL,SEKSEC
	STO	AL,HSTSEC
	STO	AL,ACTSEC
	LD	AL,#F.RDAT+040h	;Read double density
	LD	AH,RDFLAG
	OR	AH,AH
	JZ	BLKXFR		;If read required
FILL5:	RET
	SPACE	4,10
;	FLUSH - Write out active host buffer onto disk.

FLUSH:
	LD	BX,#HSTWRT
	LD	AL,[BX]
	CMP	AL,#0
	JE	FILL5		;If host buffer already on disk
	STOB	#0,[BX]
	LD	AX,HSTDSK	;Move disk and type
	STO	AX,ACTDSK
	LD	AX,HSTTRK
	STO	AX,ACTTRK
	LD	AL,HSTSEC
	STO	AL,ACTSEC
	LD	AL,#F.WRT+040h	;Write double density
;	JMP	BLKXFR
	SPACE	4,10
BLKXFR:	MOV	CL,AL
	LD	AX,#HSTBUF
	STO	AX,BUFADR
	STO	DS,BUFSEG
	MOV	AL,CL
;	JMP	FINAL

	SPACE	4,10
;	F I N A L   --  Preform final transfer processing.
;
;	ENTRY	AL = Command.
;		Act.xxx = transfer parameters.
;		NUMSEC= xfer length (if @LDR)
;	Exit	AL= 0	==> if successful
;		AL= 1	==> if Error

FINAL:	CALL	PRCDCH		;Process command, drive, cylinder
	LD	BX,#CIOPB	;Set buffer address
	STO	CX,[BX+0]	;Set command and drive
	STO	DX,[BX+2]	;Set cylinder and head
	LD	AL,ACTSEC	;Get sector
	INC	AL
	STO	AX,[BX+4]	;Set sector and N field
.ldr	if	@LDR
	LD	DL,NUMSEC
	ADD	AL,DL
	DEC	AL		;EOT = sector + (N-1)
.ldr	endif
	STO	AL,[BX+6]	;Set EOT = sector
	CMP	AH,#HMDTYP	;If memory disk
	JE	HMDFNL		
	CMP	AH,#4
	JL	:0
	JMP	hdfnl		;If hard disk
:0:	SHL	AH
	MOV	AL,AH		;SI= 2 * Type
	CBW
	MOV	SI,AX
	LD	AX,[SI+CMDTYP]
	STO	AX,[BX+7]	;Set GPL and DTL fields

	LD	AL,#MRTRY	;Set retry count
:1:	STO	AL,RTRY		;Clear retry count
	LD	AL,CIOPB+2	;Get cylinder number
	CALL	DOSEEK		;Seek to proper track
	JNZ	:3		;If seek error

	LD	AX,BUFSEG
	LD	CL,#4
	ROL	AX,CL
	MOV	BX,AX		;save lower 16 bits of paragraph
	AND	AL,#0Fh		;grab upper nibble of paragraph
	AND	BX,#0FFF0h
	ADD	BX,BUFADR
	ADC	AL,#0		;propagate carry up to upper nibble 
	OUTB	DMA		;MSB
	MOV	AL,BH
	OUTB	DMA		;Middle Byte
	MOV	AL,BL
	OUTB	DMA		;LSB

	LD	BX,#CIOPB
	LD	CX,#CIOPL	;Set command buffer length
	LD	DX,#7
	CALL	EXEC		;perform operation
	SUB	AX,#8040h
	STO	AH,ERFLAG
	JZ	:4		;If no errors

:3:	LD	AL,RTRY		;Get retry counter
	DEC	AL
	JNZ	:1		;If not permanent error
	OR	AL,#01h
	STO	AL,ERFLAG	;Set error flag
:4:	RET

;
; M-DRIVE/H Final processing
; CIOPB + 0 - Command
;	+ 2 - Track
;	+ 4 - Sector
;
HMDFNL:	
	IF	HDRIVE
	LD	AL,#MRTRY
	STO	AL,RTRY		;Initialize retry count
HMFNL1:	LD	AX,CIOPB+2	;Get track
	LD	CX,#128		;
	MUL	CX		;Track * 128 is EA
	MOV	BX,AX		;Save 
	LD	AL,CIOPB+4	;Get Sector #
	DEC	AL		;Actual is 1 less
	CALL	SET
	PUSH DI ! PUSH SI
	PUSH ES ! PUSH DS	;Save regs for string commands
	LD	SI,BUFADR	;
	LD	BX,BUFSEG	;Get buffer segment
	LD	AL,CIOPB	;Get command
	MOV	DS,BX		;
	LD	CX,#128		;128 bytes to I/O
	MOV	DL,CL		;For parity
	CLD			;Clear direction flag
	CMP	AL,#F.RDAT	;Is command read?
	JNE	HDINTO		;If write jump
;	JMP	HDOTOF
	MOV	DI,SI		;Change directions
	MOV	AX,DS
	MOV	ES,AX		; 
HDOTOF:	INB	HDATA		;Get a byte from MDRIVE
	STOSB			;Store it in buffer
	ADD	DL,AL		;Add parity
	LOOP	HDOTOF		;Loop until CX is 0 (128)
	POP DS ! POP ES		;RESTORE INDEX REGISTERS
	POP SI ! POP DI		
	CALL	PARITY		;
	INB	HDATA		;Get Parity
	SUB	AL,DL		;Check for error
	JZ	HDONE		;IF no error
	LD	AL,RTRY		;Get retry count
	DEC	AL		;Count error
	STO	AL,RTRY		;
	JNZ	HMFNL1		;Go retry		
.hdrive	ENDIF
	LD	AL,#0
	OR	AL,#1
	STO	AL,ERFLAG
HDONE:	RET
.hdrive	IF	HDRIVE
;
HDINTO:	LODSB			;Get a byte from preset buffer
	OUTB	HDATA		;To MDRIVE
	ADD	DL,AL		;Add parity
	LOOP	HDINTO		;Loop till CX = 0 (128) 	
	POP DS ! POP ES		;RESTORE INDEX REGISTERS
	POP SI ! POP DI		
	CALL	PARITY		;Set board for parity
	MOV	AL,DL		;Get parity
	OUTB	HDATA		;
	XOR	AX,AX		;Show no error
	RET			;
;
PARITY:	LD	AL,CIOPB+4	;Get sector
	DEC	AL		;Bias
	LD	BX,CIOPB+2	;Get track
;	CALL	SET		;
;	RET
SET:	;Set MDRIVE board with 3 byte AL=highest,BX=2 lowest
	OUTB	HADDR
	MOV	AL,BH
	OUTB	HADDR
	MOV	AL,BL
	OUTB	HADDR
	RET	
;
.hdrive	ENDIF

hdfnl:
	IF	HARD
	call	hdsel		;Select drive
	sto	al,erflag
	jnz	hdfnl0		;If select error
	ld	al,#mrtry
hdfnl1:	sto	al,rtry
	call	hdseek		;Seek to correct track
	call	hdxfer		;Perform hard disk transfer
	sto	al,erflag
	jz	hdfnl0		;If no errors
	dec	rtry
	jnz	hdfnl1		;If attempts left
	ld	bl,actdsk
	ld	bh,#0
	stob	#-1,[bx+hdcyl]
	endif
	LD	AL,#0
	OR	AL,#1
	STO	AL,ERFLAG
hdfnl0	RET

RTRY:	DB	0
MRTRY:	EQU	10		;Maximum retry count

;	Command buffer disk type dependent values.

CMDTYP:	;	GPL  DTL
	DB	007H,128	;Single density
	DB	00EH,255	;Double density 256 bytes
	DB	01BH,255	;Double density 512 bytes
	DB	035H,255	;Double density 1024 bytes
	SPACE	4,10
;	PRCDCH -- Process Command, Drive, Cylinder, and Head.
;
;	ENTRY	A = command.
;
;	EXIT	AH = N field (0..4).
;		CH = drive.
;		CL = command.
;		DH = head.
;		DL = cylinder.

PRCDCH:	MOV	CL,AL		;Save Command
	LD	CH,ACTDSK
	LD	DX,ACTTRK	;Get track number
	LD	AH,ACTTYP	;Get type
	CMP	AH,#HMDTYP	;If Memory disk
	JZ	CDCHMD		;Done
	CMP	AH,#MAXFTP
	JG	CDCH2		;If hard disk
	TEST	AH,#1
	JZ	CDCH1		;If single sided
	MOV	AL,DL
	AND	AL,#1
	MOV	DH,AL		;Set head
	ROL	AL
	ROL	AL
	OR	CH,AL		;Combine head with drive
	SHR	DL		;Adjust track for cylinder

CDCH1:	SHR	AH
CDCHMD:	RET

CDCH2:
.h	IF	HARD
	LD	AH,#4		;Force type = 4
	MOV	AL,DL
	if	gbc20
	and	al,#7
	shr	dx
	endif
	if	gbc10
	and	al,#3
	endif
	if	gbc26
	and	al,#7
	shr	dx
	endif
	SHR	DX		;Remove head from track
	SHR	DX
	MOV	DH,AL
	AND	CL,#00Fh
	CMP	CL,#F.RDAT
	LD	CL,#H.red
	JZ	CDCH3		;If read command
	LD	CL,#H.wrt
CDCH3:
.h	endif
	RET
	SPACE	4,10
;	Seek to specified Track/Sector
;
;	Entry	A = Track

DOSEEK:
	STO	AL,DSEKC+2
	LD	BX,#DSEKC
	LD	CX,#DSEKL
;	JMP	MOVETO


;	Move head according to command.
;
;	ENTRY	BX = address of command buffer.
;		CX = length of command buffer.
;
;	Exit	Z bit set if no error.

MOVETO:
	CALL	EXECP		;Perform seek
MVTO1:	INB	INTS
	CMP	AL,#0
	JNS	MVTO1		;if not complete
	LD	AL,#F.RSTS
	OUTB	FDCD		;request status
	LD	CX,#2
	CALL	GCMPS		;Get status
	CMP	AL,#20h
	JZ	MVTO2		;If seek complete
	LD	CL,TEMPBF	;Get true status byte
	AND	CL,#3h		;Mask disk unit
	LD	AL,ACTDSK
	CMP	AL,CL
	JNE	MVTO1		;If not proper unit
	OR	AL,#001h	;Clear zero flag
MVTO2:	RET
	SPACE	4,10
;	SPECIFY - Specify disk drive characteristics.

SPECIFY:
	LD	BX,#SPEC
	LD	CX,#LSPEC
	LD	DX,#0
	LD	AL,STEPMS
	OR	AL,#HUT
	STO	AL,[BX+1]
	JMP	EXEC		;Specify disk command

DSEKC	DB	F.SEEK,0,0
DSEKL:	EQU	*-DSEKC

SPEC	DB	F.SPEC
	VFD	4\SRT,4\HUT
	VFD	7\HLT,1\ND
LSPEC	EQU	*-SPEC
	PAGE
;	E X E C
;	Entry	BX = FWA of command buffer.
;		CX  = # of bytes to output
;		DX  = # of bytes for status
;
;	Exit	If C <> 0 then see GCMPS.

EXECP:	LD	DX,#0		;Set no status byte

EXECX:	LD	AL,ACTDSK	;Set drive into command buffer
	STO	AL,[BX+1]

EXEC:
EXEC1:	INB	FDCS
	CMP	AL,#0
	JNS	EXEC1		;if no master ready bit
	LD	AL,[BX]		;command byte
	OUTB	FDCD		;to controller
	INC	BX
	LOOP	EXEC1		;If more bytes
	OR	CX,DX
	JZ	:30		;if no status bytes
EXEC2:	INB	INTS
	CMP	AL,#0
	JNS	EXEC2		;If operation not complete
	SPACE	4,10
;	Get completion status.
;
;	Entry	CX = # of status bytes to read
;
;	Exit	TEMPBF = status bytes read in.
;		A = [TEMPBF] and 0F8h.
;		Flags set according to above value in A.

GCMPS:
	LD	BX,#TEMPBF	;Set status buffer address
GCMPS2:	INB	FDCS
	CMP	AL,#0
	JNS	GCMPS2		;if not ready
	INB	FDCD		;Get status byte
	STO	AL,[BX]
	INC	BX
	LOOP	GCMPS2		;If more bytes
	LD	AX,TEMPBF	;Get two status bytes
	AND	AL,#0F8h
:30	RET