TITLE 'CBIOS FOR CP/M 2.2'
	PAGE	60
; CP/M BASIC INPUT/OUTPUT OPERATING SYSTEM (BIOS)
; TARBELL ELECTRONICS
; 2.2 VERSION OF 12-5-79
;	MODIFIED BY RICHARD B. KOLBLY
;			10-01-80
;			10-31-80
;
; THIS BIOS MODULE IS THE CPM V2.2 
; CBIOS. THIS BIOS READS SINGLE DENSITY 
; DISK.. TRACK 0 = SINGLE DENSITY (IBM COMPATABLE)
; TRACKS 1 - 76 SINGLE DENSITY 52 SECTORS.
;
; THIS SECTION DEFINES THE I/O PORTS AND
; STATUS BITS.  BY SETTING THE PROPER VALUES
; FOR THE EQU STATEMENTS, THE I/O MAY BE
; AUTOMATICALLY RECONFIGURED TO FIT MOST
; SITUATIONS.  THE TRUE AND FALSE ONES
; CONTROL CONDITIONAL ASSEMBLIES OF DIFFERENT
; SECTIONS OF I/O ROUTINES TO FIT DIFFERENT
; INTERFACE REQUIREMENTS.

TRUE	EQU  0FFFFH	;DEFINE VALUE OF TRUE.
FALSE	EQU  NOT TRUE	;DEFINE VALUE OF FALSE.

;***************************************************
;*** THIS BEGINS THE AREA WHICH REQUIRES CHANGES ***
;***      FOR DIFFERENT CONSOLE I/O SYSTEMS      ***
;***************************************************

MSIZE	EQU  56		;MEMORY SIZE IN KBYTES.

NDISK	EQU  2		;DEFINES THE NUMBER DRIVES IN SYSTEM.
CDATA	EQU  0		;USED TO CLEAR CONSOLE STATUS.
HLAB	EQU  0		;8 FOR HD LD AT BEG OF SEEK.
STPRAT	EQU  3		;RATE 1=6MS, 2=10MS, 3=20MS.

;*******************************************************
;*** THIS IS THE END OF THE AREA WHICH NORMALLY NEED ***
;***     BE CHANGED FOR MOST CONSOLE I/O SYSTEMS     ***
;*******************************************************

RDYLO	EQU  TRUE	;STATUS READY WHEN LOW.
RDYHI	EQU  NOT RDYLO
DISK	EQU  0F8H	;DISK BASE ADDRESS.
DCOM	EQU  DISK	;DISK COMMAND PORT.
DSTAT	EQU  DISK	;DISK STATUS PORT.
TRACK	EQU  DISK+1	;DISK TRACK PORT.
SECTP	EQU  DISK+2	;DISK SECTOR PORT.
DDATA	EQU  DISK+3	;DISK DATA PORT.
WAIT	EQU  DISK+4	;DISK WAIT PORT.
DCONT	EQU  DISK+4	;DISK CONTROL PORT.	

RTCNT	EQU  10		;RETRY COUNT.
IOBYTE	EQU  3		;ADDRESS OF I/O BYTE.
FF	EQU  0CH	;ASCII FORM FEED CHARACTER
LF	EQU  0AH	;ASCII LINE FEED CHARACTER
CR	EQU  0DH	;ASCII CARRIAGE RETURN
;
; VALUES OF I/O FUNCTIONS
;
@CONIN	EQU  0F803H	;GET CHARACTER FROM CONSOLE
@READER EQU  0F806H	;GET CHARACTER FROM READER
@CONOT  EQU  0F809H	;WRITE TO CONSOLE DEVICE
@PUNCH  EQU  0F80CH	;WRITE TO PUNCH DEVICE
@LIST   EQU  0F80FH	;CHARACTER TO LIST DEVICE
@CONST  EQU  0F812H	;GET STATUS OF CONSOLE KEYBOARD
@PRSTAT EQU  0F815H	;STATUS OF LIST DEVICE
@PMSG   EQU  0F818H	;PRINT MESSAGE IN (HL) TIL ZERO
@ERROR  EQU  0F81BH	;ERROR REPORTING ROUTINE
;

CBASE	EQU  (MSIZE-20)*1024  	;BIAS FOR LARGER THAN 20K.
CPMB	EQU  CBASE+3400H	;START OF CPM 2.2
BDOS	EQU  CPMB+806H		;START OF BDOS 2.2.
BIOS	EQU  CPMB+1600H		;START OF CBIOS IO.
CDISK	EQU  4			;LOCATION 4 IS CURRENT DISK.
NSECTS	EQU  17			;NUMBER OF SECTORS IN IT.

	ORG  CPMB+16
;
SMSG:   DB   0DH,0AH,0DH,'SBMS/K6HIJ',0AH,0DH
	DB   MSIZE/10+'0',MSIZE MOD 10+'0'
	DB   'K CP/M V2.2 of 10-31-80',0
;
; BOOT
; THIS SECTION IS EXECUTED WHENEVER RESET AND RUN
; IS PUSHED, AFTER THE COLDSTART LOADER READS IN
; THE CPM SYSTEM.
;
BOOT:	LXI  SP,80H	;SET STACK POINTER.
	JMP  BOOTF	;FINISH BOOT.
	ORG  BIOS-64	;HIDE REST OF BOOT HERE.
BOOTF:
	XRA  A		;CLEAR SCRATCH AREA.
	STA  CDISK	;SELECT DRIVE ZERO
	STA  LATCH	;SET LATCH FOR DRIVE A.
	LXI  H,IOBYTE	;POINT TO IOBYTE.
	MVI  M,01H	;SET UP IOBYTE.
	MVI  B,ENDZ-STARTZ    ;GET LENGTH OF ZERO AREA.
	LXI  H,STARTZ	;GET SCRATCH ADDRESS.
BOOTL:	MOV  M,A	;PUT ZERO IN MEMORY.
	INX  H		;INCREMENT POINTER.
	DCR  B		;DECREMENT COUNTER.
	JNZ  BOOTL	;LOOP TILL DONE.
	IN   CDATA	;CLEAR CONSOLE STATUS.
	LXI  H,SMSG	;POINT TO SIGN ON.
PMSG1:	MOV  A,M	;GET A BYTE OF THE MESSAGE
	INX  H		;BUMP MEMORY POINTER.
	ORA  A		;IS IT A ZERO?
	JZ   GOCPM	;YES, WE ARE DONE, JMP TO CPM.
	MOV  C,A	;NOPE, PRINT MORE MESSAGE.
	CALL @CONOT	;USE THE CONOT ROUTINE.
	JMP  PMSG1	;AND LOOP TILL DONE.

	ORG  BIOS		;START OF CBIOS STRUCTURE.
;
; I/O JUMP VECTOR
; THIS IS WHERE CPM CALLS WHENEVER IT NEEDS
; TO DO ANY INPUT/OUTPUT OPERATION.
; USER PROGRAMS MAY USE THESE ENTRY POINTS
; ALSO, BUT NOTE THAT THE LOCATION OF THIS
; VECTOR CHANGES WITH THE MEMORY SIZE.
;
DMAENT:	JMP  BOOT		;FROM SBOOT LOADER,CHANGED FOR DMA.
WBOOTE:	JMP  WBOOT		;FROM WARM BOOT.
	JMP  @CONST		;CHECK CONSOLE KB STATUS.
	JMP  @CONIN		;READ CONSOLE CHARACTER.
	JMP  @CONOT		;WRITE CONSOLE CHARACTER.
	JMP  LIST		;WRITE LISTING CHAR.
	JMP  @PUNCH		;WRITE PUNCH CHAR.
	JMP  @READER		;READ READER CHAR.
	JMP  HOME		;MOVE DISK TO TRACK ZERO.
	JMP  SELDSK		;SELECT DISK DRIVE.
	JMP  SETTRK		;SEEK TO TRACK IN REG A.
	JMP  SETSEC		;SET SECTOR NUMBER.
	JMP  SETDMA		;SET DISK STARTING ADR.
	JMP  READ		;READ SELECTED SECTOR.
	JMP  WRITE		;WRITE SELECTED SECTOR.
	JMP  @PRSTAT		;LIST STATUS CHECK.
	JMP  SECTRAN		;SECTOR TRANSLATE ROUTINE.

; THIS SECTION DEFINES THE THE DISK PARAMETERS
; NOTE:
; IF YOU HAVE THE MACRO ASSEMBLER (MAC) FROM
; DIGITAL RESEARCH, YOU MAY ELIMINATE THIS SECTION
; STARTING AT **AA** TO **BB** AND USE THE MACRO
; FILE "DISKDEF" TO CUSTOM TAILOR YOUR SYSTEM TO
; ALLOW DIFFERENT TYPES OF DRIVES OR MORE THAN 4
; DRIVES.
;
;**AA**
;
DPBASE	EQU  $			;BASE OF DISK PARAMETER BLOCK
DPE0:	DW   XLT0,0000H		;TRANSLATE TABLE
	DW   0000H,0000H	;SCRATCH AREA
	DW   DIRBUF,SDTAB+2	;DIR BUFF, PARM BLOCK
	DW   CSV0,ALV0		;CHECK, ALLOC VECTORS
;
DPE1:	DW   XLT1,0000H
	DW   0000H,0000H
	DW   DIRBUF,DPB1
	DW   CSV1,ALV1
;
;THE FOLLOWING DESCRIBES THE DISK PHYSICAL
;NATURE, SUCH AS SECTORS/TRACK,DIRECTORY SIZE.
;THE FOLLOWING TABLE DEFINES A SINGLE DENSITY DRIVE.
;
SDTAB:	EQU  $			;ONE OF 4 DISK PARM. BLOCKS
	DW   XLT0		;USE SINGLE DENSITY TRANSLATE TAB.
	DW   26			;SECTORS/TRACK
	DB   3			;BLOCK SHIFT
	DB   7			;BLOCK MASK
	DB   0			;EXTNT MASK
	DW   242		;DISK SIZE - 1
	DW   63			;DIRECTORY MAX.
	DB   192		;ALLOC0
	DB   0			;ALLOC1
	DW   16			;CHECK SIZE
	DW   2			;NUMBER OF SYSTEM TRACKS
;
;SECTOR TRANSLATION TABLE
;
XLT0	EQU  $			;START OF TRANS. TABLE
	DB   1,7,13,19,25
	DB   5,11,17,23,3
	DB   9,15,21,2,8
	DB   14,20,26,6,12
	DB   18,24,4,10,16,22
;
DPB1	EQU  SDTAB+2		;EQUIVALENT PARAMETERS
XLT1	EQU  XLT0		;SAME TRANSLATE TABLE
;
;**BB**
;
;
; WARM-BOOT:  READ ALL OF CPM BACK IN
; EXCEPT BIOS, THEN JUMP TO CCP.
;
WBOOT:	LXI  SP,80H	;SET STACK POINTER.
	LDA  CDISK	;SAVE DISK NUMBER.
	STA  TEMP
	MVI  C,0	;SELECT DISK 0.
	CALL SELDSK
	CALL HOME	;MOVE TO TRACK ZERO.
	JNZ  RDERR1	;IF ERROR, PRINT MESSAGE.
	MVI  D,NSECTS	;GET # SECTORS FOR CPM READ.
	LXI  B,2	;TRACK (B)=0, SECTOR (C)=2.
	LXI  H,CPMB	;GET STARTING ADDRESS.
RDBLK:	MOV A,B		;GOTO TRACK IN B.
	CALL SEEK
	JNZ  RDERR1	;IF ERROR, PRINT MESSAGE.
	MOV  A,C	;READ STARTING AT SECTOR IN C.
	CALL READ1
RBLK1:	JNZ  RDERR1	;IF ERROR, PRINT MESSAGE.
	DCR  D		;DECREMENT SECTOR COUNT.
	JZ   ALDON	;ALL DONE WHEN ZERO.
	INR  C		;INCREMENT SECTOR NUMBER.
	MOV  A,C	;IF SECTOR NUMBER
	CPI  27		; IS NOT 27,
	JC   RBLK2	; HOP OUT OF LOOP.
	MVI  C,1	;OTHERWISE, RESET SECTOR=1
	INR  B		; INCREMENT TRACK NUMBER,
	JMP  RDBLK	; AND READ NEXT TRACK.
ALDON:	LDA  TEMP	;RESTORE DISK NUMBER.
	STA  CDISK
	JMP  GOCPM	;GO BACK TO CPM.

RBLK2:	CALL READ2	;READ ANOTHER TRACK.
	JMP  RBLK1

GOCPM:
;
; SET UP JUMPS INTO CP/M IN LOWER MEMORY.
;
	MVI  A,0C3H	;PUT JMP TO WBOOT
	STA  0		;ADR AT ZERO.
	LXI  H,WBOOTE
	SHLD 1
	STA  5
	LXI  H,BDOS	;PUT JUMP TO BDOS
	SHLD 6		;AT ADR 5,6,7.
	LXI  H,80H	;SET DEFAULT DMA ADR.
	SHLD DMAADD
	LDA  CDISK	;GET DISK NUMBER TO
	MOV  C,A	;PASS TO CCP IN C.
	JMP  CPMB	;JUMP TO CCP.
;
; LISTING ROUTINE - REQUIRED TO HANDLE FORMFEED CHARACTERS
;
LIST:	LDA	IOBYTE	;GET STATUS
	ANI	40H	;SEE IF IT IS TTY
	JNZ	@LIST	;IF NOT, NO SPECIAL HANDLING
	MOV	A,C	;GET CHARACTER TO BE LISTED
	CPI	FF	;IS IT A FORM FEED?
	JZ	FFEED	;YES, DO A FORM FEED
	CPI	LF	;IS IT LINE FEED?
	JNZ	@LIST	;NO, SO LIST IT
LIST1:	LDA	COUNT	;GET LINES COUNT
	INR	A	;UP THE COUNT
	CPI	66	;MAX LINES PER PAGE
	JNZ	$+4	;NOT MAX, CONTINUE
	XRA	A	;ZERO COUNT
	STA	COUNT	;SAVE FOR NEXT TIME
	JMP	@LIST	;NOW SEND LF

;
FFEED:	LDA	COUNT	;GET COUNT
	ORA	A	;SET FLAGS
	RZ		;ZERO,MUST BE AT TOP OF FORM ALREADY
	MVI	C,LF	;GET LINE FEED TO SEND
	CALL	LIST1	;SEND TO PRINTER
	JMP	FFEED	;KEEP SENDING LF'S TIL TOP OF FORM
;
; SELECT DISK NUMBER ACCORDING TO REGISTER C.
;
SELDSK:
	LXI  H,0		;SET UP FOR ERROR CODE
	MOV  A,C		;GET NEW DRIVE.
	CPI  NDISK		;CALLING UNDEFINED DRIVE ?
	RNC			;IF NO CY, H,L TELLS CPM YES.
	STA  CDISK		;WE ARE OK, SAVE NEW DISK NUMB.
	LXI  H,DISKNO		;GET OLD DRIVE NUMBER.
SELMOR:
	MOV  A,M	;GET OLD DISK NUMBER.
	MOV  E,A	;PUT OLD DISK NO. IN D&E.
	MVI  D,0
	LXI  H,TRTAB	;GET ADDRESS OF TRACK TABLE.
	PUSH H		;SAVE ADDRESS OF TRTAB.
	DAD  D		;ADD DISK NO. TO ADDRESS.
	IN   TRACK	;READ 1771 TRACK REGISTER.
	MOV  M,A	;PUT INTO TABLE.
	MOV  A,C	;GET NEW DISK NUMBER.
	MOV  E,A	;PUT NEW DISK NO. IN D&E.
	POP  H		;RESTORE ADDRESS OF TRTAB.
	DAD  D		;ADD DISK NO. TO ADDRESS.
	MOV  A,M	;GET NEW TRACK NUMBER.
	OUT  TRACK	;PUT INTO 1771 TRACK REG.
SELD1:	MOV  A,C	;UPDATE OLD DISK NUMBER.
	STA  DISKNO
	CMA
	ADD  A		;PUT BITS 1&2 AT 4&5.
	ADD  A
	ADD  A
	ADD  A
	ORI  2
	STA  LATCH	;SAVE NEW LATCH CODE.
;
;SELECT DRIVE AS A FUNCTION OF H,L
;
PARINDX:LHLD DISKNO		;LOAD DISK NUMBER AND ZERO BYTE
	LXI  D,DPBASE		;POINT TO DISK PARM START.
	DAD  H			;*2
	DAD  H			; *4
	DAD  H			;  *8
	DAD  H			;   *16
	DAD  D			;COMPUTE INDEX FOR THE DRIVE
	XRA  A		;SET A = 0.
	RET		;RETURN FROM SELDSK.
;
; MOVE DISK TO TRACK ZERO.
;
HOME:	MVI  C,0	;SEEK TO TRACK ZERO.
	MVI  A,0D0H	;RESTORE COMMAND
	OUT  DCOM	;TELL CONTROLLER.
;
; SET TRACK NUMBER TO WHATEVER IS IN REGISTER C.
; ALSO PERFORM MOVE TO THE CORRECT TRACK (SEEK).

SETTRK:
	PUSH H		;SAVE H&L.
	LHLD LATCH	;GET NEW & OLD LATCH.
	MOV  A,L	;GET NEW LATCH.
	OUT  DCONT	;SELECT DRIVE NOW.
	STA  CLATCH	;REMEMBER CURRENT LATCH.
	CMP  H		;IS NEW SAME AS OLD?
	MVI  A,0FFH	;IF NOT, SET FLAG = FF.
	JNZ  SFLAG
	CMA		;IF NEW = OLD, FLAG = 0.
SFLAG:	STA  HLSF	;SET HEAD-LOAD/SELECT FLAG.
	POP  H		;RESTORE H&L.
	MOV  A,C	;GET NEW TRACK NUMBER.
	STA  TRK	;UPDATE OLD WITH NEW.
;
; MOVE THE HEAD TO THE TRACK IN REGISTER A.
;
SEEK:	PUSH B		;SAVE B&C.
	MOV  B,A	;SAVE DESTINATION TRACK.
	MVI  A,RTCNT	;GET RETRY COUNT.
	STA  SERCNT	;STORE IN ERROR COUNTER.
	PUSH PSW
SRETRY:	POP  PSW
	IN   TRACK	;READ PRESENT TRACK NO.
	CMP  B		;SAME AS NEW TRACK NO.?
	JNZ  NOTHR	;JUMP IF NOT THERE.
THERE:	POP  B		;RESTORE B&C.
	RET		;RETURN FROM SEEK.
NOTHR:

;DELAY LOOP TO ALLOW TUNNEL
;ERASE TO END DURING WRITE.
;
	MVI  A,0D0H	;COUNT = 208
BUSY1:	DCR  A		;LOOP
	JNZ  BUSY1	; TILL = ZER0
	MOV  A,B	;RESTORE A FROM B.
	OUT  DDATA	;TRACK TO DATA REGISTER.
BUSY:	IN   DSTAT	;READ DISK STATUS.
	RRC		;LOOK AT BIT 0.
	JC   BUSY	;WAIT TILL NOT BUSY.
	MVI  A,14H+STPRAT+HLAB  ;GET STEP RATE, DO
	OUT  DCOM	;SEEK WITH VERIFY.
	IN   WAIT	;WAIT FOR INTRQ.
	IN   DSTAT	;READ STATUS.
	ANI  98H	;LOOK AT BITS.
	JZ  THERE	;OK IF ZERO.
	PUSH PSW
	LDA  SERCNT	;GET ERROR COUNT.
	DCR  A		;DECREMENT COUNT.
	JZ   DABRT
	STA  SERCNT
	JMP  SRETRY
DABRT:	POP	PSW
	CALL  TP1ERR
	POP	B
DABRT1:	LXI	D,DABORT
	CALL	PRINT
	JMP	ABORT

TP1ERR:	RLC
	PUSH	PSW
	LXI	D,MSG1
	CC	PRINT
	POP	PSW
	RLC
	PUSH	PSW
	LXI	D,MSG2
	CC	PRINT
	POP	PSW
	RLC
	PUSH	PSW
	LXI	D,MSG3
	CC	PRINT
	POP	PSW
	RLC
	PUSH	PSW
	LXI	D,MSG6
	CC	PRINT
	POP	PSW
	RLC
	PUSH	PSW
	LXI	D,MSG4
	CC	PRINT
	POP	PSW
	RLC
	PUSH	PSW
	LXI	D,MSG5
	CC	PRINT
	POP	PSW
	RET

;
; SET DISK SECTOR NUMBER.
;
SETSEC:  MOV  A,C	;GET SECTOR NUMBER.
         STA  SECT	;PUT AT SECT # ADDRESS.
         RET		;RETURN FROM SETSEC.
;
;TRANSLATE THE SECTOR GIVEN B,C
;USING THE TRANSLATE TABLE
;GIVEN BY D,E
;
SECTRAN:
	XCHG			;H,L = TRANS
	DAD  B			;H,L = TRANS (SECTOR)
	MOV  L,M		;L   = TRANS (SECTOR)
	MVI  H,0		;CLEAR REG H
	RET			;H,L = TRANSLATED SECTOR
;
; SET DISK DMA ADDRESS.
;
SETDMA:  MOV  H,B	;MOVE B&C TO H&L.
         MOV  L,C
         SHLD DMAADD	;PUT AT DMA ADR ADDRESS.
         RET		;RETURN FROM SETDMA.
;
; HDLD - GET HEAD-LOAD BIT IF REQUIRED.
;
HDLD:	LDA  HLSF	;GET HEAD-LOAD FLAG.
	ORA  A		;IS A = ZERO?
	JZ   HDLD1	;HOP IF SO.
	CMA		;SET A = 0.
	STA  HLSF	;SET FLAG = 0 IF NOT.
HDLDY:	MVI  A,4	;SET BIT TO LOAD HEAD.
	RET		;RETURN FROM HDLD.
HDLD1:	IN   DSTAT	;READ 1771 STATUS.
	ANI  20H	;LOOK AT HL BIT.
	JZ   HDLDY	;LOAD IF NOT LOADED.
	XRA  A		;OTHERWISE, A=0.
	RET		;RETURN FROM HDLD.

; READ A SECTOR WITHOUT LOADING HEAD FIRST.
;
READ1:	OUT SECTP	;SET SECTOR NUMBER INTO 1771.
	MVI  A,8CH	;GET CODE FOR READ W/O HLD.
	JMP  READE	;READ A SECTOR.
READ2:	OUT SECTP
	MVI  A,88H
	JMP  READE

;
; READ THE SECTOR AT SECT, FROM THE PRESENT TRACK.
; USE STARTING ADDRESS AT DMAADD.
;
READ:	MVI  A,RTCNT	;GET RETRY COUNT.
RRETRY: 	;STOR IN ERROR CTR.
	CALL  DSKSET
	ADI   88H
READE:	OUT  DCOM	;SEND COMMAND TO 1771.
RLOOP:	IN   WAIT	;WAIT FOR DRQ OR INTRQ.
	ORA  A		;SET FLAGS.
	JP   RDDONE	;DONE IF INTRQ.
	IN   DDATA	;READ A DATA BYTE FROM DISK.
	MOV  M,A	;PUT BYTE INTO MEMORY.
	INX  H		;INCREMENT MEMORY POINTER.
	JMP  RLOOP	;KEEP READING.
RDDONE:
	IN   DSTAT	;READ DISK STATUS.
	ANI  9CH	;LOOK AT ERROR BITS.
	RZ		;RETURN IF NONE.
	CALL ERCHK	;CHECK FOR SEEK ERROR.
	LDA  ERCNT	;GET ERROR COUNT.
	DCR  A		;DECREMENT COUNT.
	JNZ  RRETRY	;TRY TO READ AGAIN.
	JMP  DABRT1

RDERR:	RLC
	PUSH	PSW
	LXI	D,MSG1
	CC	PRINT
	POP	PSW
	RLC
	RLC
	RLC
	PUSH	PSW
	LXI	D,MSG7
	CC	PRINT
	POP	PSW
	RLC
	PUSH	PSW
	LXI	D,MSG4
	CC	PRINT
	POP	PSW
	RLC
	PUSH	PSW
	LXI	D,MSG5
	CC	PRINT
	POP	PSW
	RET
RDERR1:	MVI	C,'B'
	CALL	@CONOT
	JMP	0E000H
PRINT	PUSH	H
	MVI	C,09
	CALL	BDOS
	POP	H
	RET

ABORT:	MVI	A,10
	STA	ERCNT
	STA	SERCNT
	MVI	A,1
	JMP	WBOOT

;
; ERCHK - CHECK FOR RECORD NOT FOUND ERROR.
;
ERCHK:	MOV  D,A	;SAVE ERROR BITS ON STACK.
	ANI  10H	;IF RECORD NOT FOUND,
	JNZ  CHKSK	;DO A CHECK ON SEEK.
	MOV  A,D	;RESTORE ERROR BITS.
	ORA  A
	RET		;AND RETURN.
;CHECK FOR SEEK TO CORRECT TRACK,
;AND CHANGE IF NECESSARY.
CHKSK:	MVI  A,0C4H	;SEND COMMAND TO 1771
	OUT  DCOM	;TO READ ADDRESS.
	IN   WAIT	;WAIT FOR DRQ OR INTRQ.
	IN   DDATA	;READ THE TRACK ADDRESS.
	MOV  B,A	;SAVE IN REGISTER B.
CHKS2:  IN   WAIT	;WAIT FOR INTRQ.
	ORA  A
	JP   CHKS3	;NOT IF DRQ.
	IN   DDATA	;READ ANOTHER BYTE.
	JMP  CHKS2	;DO IT AGAIN.
CHKS3:	IN   DSTAT	;READ DISK STATUS.
	ANI  09CH
	JZ   CHKS4	;READ ADR OK IF 0.
	PUSH D
	CALL RDERR
	CALL HOME	;OTHERWISE, HOME FIRST.
	POP  D
	JMP  CHKS5
CHKS4:	MOV  A,B	;UPDATE TRACK REGISTER.
	OUT  TRACK
CHKS5:	LDA  TRK	;GET REQUIRED TRACK NO.
	CALL SEEK	;MOVE THE HEAD TO IT.
	MOV  A,D
	ORA A
	RET
;
;DISK SET UP ROUTINE.
;THIS ROUTINE IS COMMON TO
;BOTH THE READ AND WRITE
;ROUTINES.
;
DSKSET:
	STA  ERCNT	;STORE IN ERROR CTR.
	MVI  A,0D0H	;CAUSE INTERRUPT.
	OUT  DCOM
	XTHL		;SOME
	XTHL		; DELAY
	LHLD DMAADD	;GET STARTING ADDR.
	LDA  SECT	;GET SECTOR NUMBER.
	OUT  SECTP	;SET SECTOR INTO 1771.
	JMP HDLD	;GET HEAD-LOAD BIT?
;
; WRITE THE SECTOR AT SECT, ON THE PRESENT TRACK.
; USE STARTING ADDRESS AT DMAADD.
;
WRITE:	MVI  A,RTCNT	;GET RETRY COUNT.
WRETRY:	CALL DSKSET	;SET UP DISK.
	ADI  0A8H	;ADD CODE TOR WRITE.
WRITE2:	OUT  DCOM
WLOOP:	IN   WAIT	;WAIT FOR READY.
	ORA  A		;SET FLAGS.
	JP   WDONE	;HOP OUT WHEN DONE.
	MOV  A,M	;GET BYTE FROM MEM.
	OUT  DDATA	;WRITE ONTO DISK.
	INX  H		;INCREMENT MEM PTR.
	JMP  WLOOP	;KEEP WRITING.
WDONE:
	IN   DSTAT	;READ DISK STATUS.
	ANI  0E4H	;LOOK AT THESE BITS.
	RZ		;RETURN IF NO ERR.
	CALL ERCHK	;CHECK/CORRECT SEEK ERR.
	CALL TP1ERR
	LDA  ERCNT	;GET ERROR COUNT.
	DCR  A		;DECREMENT COUNT.
	JNZ  WRETRY	;TRY TO WRITE AGAIN.
	JMP  DABRT1

;
;
MSG1:	DB	CR,LF,'NOT READY','$'
MSG2:	DB	CR,LF,'WRITE PROTECT','$'
MSG3:	DB	CR,LF,'WRITE FAULT','$'
MSG4:	DB	CR,LF,'CRC ERROR','$'
MSG5:	DB	CR,LF,'LOST DATA','$'
MSG6:	DB	CR,LF,'SEEK ERROR.','$'
MSG7:	DB	CR,LF,'NOT FOUND','$'
DABORT:	DB	CR,LF,'ABORTED','$'
;
;NOTE:  AS THERE ARE ONLY SIX (6) SECTORS
;AVAILABLE FOR CBIOS ON THE SECOND SYSTEM TRACK (1),
;THE LAST ADDRESS BEFORE THIS POINT SHOULD BE NO
;GREATER THAN THE CBIOS STARTING ADDRESS + 037F (HEX).
;THIS WILL NORMALLY BE XD7F (HEX).
;
; BIOS SCRATCH AREA
;
; THE NEXT SEVERAL BYTES, BETWEEN STARTZ AND
; ENDZ, ARE SET TO ZERO AT COLD BOOT TIME.
;
STARTZ:
DMAADD:	DW   0000H	;DISK TRANSFER ADDRESS	
TRK:	DB   0		;CURRENT TRACK NUMBER.
SECT:	DB   1		;CURRENT SECTOR NUMBER.
DISKNO:	DB   0		;DISK NUMBER
	DB   0
PDISK:	DB   0

; SPECIAL FLAGS.
HLSF:	DB   0		;HEAD-LOAD SELECT FLAG.
LFCNT:	DB   0		;PAGING LINE-FEED COUNT.
;
; TRTAB - DISK TRACK TABLE - PRESENT POSITION OF
;	HEADS FOR UP TO 4 DRIVES.
;
TRTAB:	DB   00
	DB   00
COUNT:  DB   00		;LINE COUNT
ENDZ:			;END OF ZEROED AREA.

ERCNT:	DS   1		;ERROR COUNT FOR RETRIES.
SERCNT:	DS   1		;SEEK RETRY COUNTER.
TEMP:	DS   1		;TEMPORARY STORAGE.
LATCH:	DS   1		;NEW CODE FOR LATCH.
CLATCH:	DS   1		;CURRENT CODE IN LATCH.
BEGDAT	EQU  $
DIRBUF:	DS   128	;DIRECTORY BUFFER
ALV0:	DS   31
CSV0:	DS   24
ALV1:	DS   31
CSV1:	DS   24
ALV2:	DS   31
CSV2:	DS   24
ALV3:	DS   31
CSV3:	DS   24
ENDDAT	EQU  $
DATSIZ	EQU  $-BEGDAT		;TOTAL SIZE OF DISK PARM STORAGE.
;
	END