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MS-DOS/v1.25/source/IO.ASM
Rich Turner fce0f75959 MS-DOS v1.25 Release
2018-09-21 17:51:26 -07:00

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NASM
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; I/O System for 86-DOS version 1.20 and later. Revised 8-02-82.
;
; Assumes a CPU Support card at F0 hex for character I/O,
; with disk drivers for SCP, Tarbell, or Cromemco controllers.
;
; Select whether console input is interrupt-driven or polled.
INTINP: EQU 1
;
; Select whether the auxiliary port is the Support Card parallel port
; or on channel 1 of a Multiport Serial card addressed at 10H.
PARALLELAUX: EQU 1
SERIALAUX: EQU 0
;
; Select whether the printer is connected to the Support card parallel
; output port (standard) or channel 0 of a Multiport Serial card
; addressed at 10H.
PARALLELPRN: EQU 1
SERIALPRN: EQU 0
;
; If the Multiport Serial was chosen for either the auxiliary or the
; printer, select the baud rate here. Refer to Multiport Serial manual
; page 11 to pick the correct value for a given baud rate.
PRNBAUD:EQU 7 ; 1200 baud
AUXBAUD:EQU 0FH ; 19200 baud
;
; Select disk controller here.
SCP: EQU 1
TARBELLSD: EQU 0
TARBELLDD: EQU 0
CROMEMCO4FDC: EQU 0
CROMEMCO16FDC: EQU 0
;
; Select if you want a special conversion version which can read/write
; both the new Microsoft format and the old SCP format.
; For a two drive system, drives A and B are the new Microsoft format,
; and drives C and D are the old SCP format (where C is the same physical
; drive as A, and D is the same drive as B). CONVERT has no effect
; on 5.25-inch drives.
CONVERT:EQU 1
;
; Select disk configuration:
LARGE: EQU 1 ; Large drives.
COMBIN: EQU 0 ; Two 8-inch and one 5.25-inch.
SMALL: EQU 0 ; Three 5.25-inch drives.
CUSTOM: EQU 0 ; User defined.
;
; If 8-inch drives are PerSci, select FASTSEEK here:
; (Fastseek with Tarbell controllers doesn't work yet).
FASTSEEK: EQU 1
;
; For double-density controllers, select double-sided operation of
; 8-inch disks in double-density mode.
LARGEDS: EQU 0
;
; For double-density controllers, select double-sided operation of
; 5.25-inch disks in double-density mode.
SMALLDS: EQU 0
;
; Use table below to select head step speed. Step times for 5" drives
; are double that shown in the table. Times for Fast Seek mode (using
; PerSci drives) is very small - 200-400 microseconds.
;
; Step value 1771 1793
;
; 0 6ms 3ms
; 1 6ms 6ms
; 2 10ms 10ms
; 3 20ms 15ms
;
STPSPD: EQU 0
;
; ****** End of selections ********************************************
;
BIOSSEG:EQU 40H ; I/O system segment.
BIOSLEN:EQU 2048 ; Maximum length of I/O system.
DOSLEN: EQU 8192 ; Maximum length of MS-DOS.
QSIZE: EQU 80 ; Input queue size.
PBUFSIZ:EQU 128 ; Size of print buffer
BASE: EQU 0F0H ; CPU Support card base port number.
SIOBASE:EQU 10H ; Base port number of Multiport Serial card.
STAT: EQU BASE+7 ; Serial I/O status port.
DATA: EQU BASE+6 ; Serial I/O data port.
DAV: EQU 2 ; Data available bit.
TBMT: EQU 1 ; Transmitter buffer empty bit.
SERIAL: EQU SERIALPRN+SERIALAUX
STCDATA:EQU BASE+4 ; Ports for 9513 Timer chip.
STCCOM: EQU BASE+5
IF SERIALAUX
AUXSTAT:EQU SIOBASE+3
AUXDATA:EQU SIOBASE+2
ENDIF
IF PARALLELAUX
AUXSTAT:EQU BASE+13
AUXDATA:EQU BASE+12
ENDIF
IF SERIALPRN
PRNSTAT:EQU SIOBASE+1
PRNDATA:EQU SIOBASE+0
ENDIF
IF PARALLELPRN
PRNSTAT:EQU BASE+13
PRNDATA:EQU BASE+12
ENDIF
ORG 0
PUT 100H
JMP INIT
JMP STATUS
JMP INP
JMP OUTP
JMP PRINT
JMP AUXIN
JMP AUXOUT
JMP READ
JMP WRITE
JMP DSKCHG
JMP SETDATE
JMP SETTIME
JMP GETTIME
JMP FLUSH
JMP MAPDEV
MAPDEV:
RET L
INIT:
XOR BP,BP ; Set up stack just below I/O system.
MOV SS,BP
MOV SP,BIOSSEG*16
IF INTINP-1
MOV AL,0FFH ; Mask all interrupts.
OUTB BASE+3
ENDIF
IF INTINP
DI ; Set up keyboard interrupt vector.
MOV [BP+64H],KBINT
MOV [BP+66H],CS
EI
ENDIF
MOV [BP+4*38H],PRNFCB
MOV [BP+4*38H+2],CS
PUSH CS
POP DS
;
; Initialize time-of-day clock.
;
MOV SI,STCTAB
MOV CX,4 ;Initialize 4 registers
UP
INITSTC:
LODB
OUT STCCOM ;Select register to initialize
LODB
OUT STCDATA
LODB
OUT STCDATA
LOOP INITSTC
IF SERIAL
MOV CX,4
SERINIT:
LODB
OUT SIOBASE+1
OUT SIOBASE+3
LOOP SERINIT
LODB ;Baud rate for channel 0
OUT SIOBASE+8
LODB ;Baud rate for channel 1
OUT SIOBASE+9
ENDIF
;
; Move MS-DOS down to the first segment just above the I/O system.
;
MOV SI,BIOSLEN ; Source points to where MS-DOS currently is.
MOV AX,DOSSEG ; Destination is beginning of DOSSEG.
MOV ES,AX
SUB DI,DI
MOV CX,DOSLEN/2 ; CX is number of words to move.
REP
MOVSW
MOV SI,INITTAB
MOV DX,1 ; Do auto memory scan.
CALL 0,DOSSEG
;
; Change disk read and write vectors (INT 37 and INT 38) to go to
; DIRECTREAD and DIRECTWRITE rather than READ and WRITE.
;
SUB BP,BP
MOV W,[BP+37*4],DIRECTREAD
MOV W,[BP+38*4],DIRECTWRITE
MOV DX,100H
MOV AH,26 ;Set DMA address
INT 33
MOV CX,[6] ;Get size of segment
MOV BX,DS ;Save segment for later
;
; DS must be set to CS so we can point to the FCB.
;
MOV AX,CS
MOV DS,AX
MOV DX,FCB ;File Control Block for COMMAND.COM
MOV AH,15
INT 33 ;Open COMMAND.COM
OR AL,AL
JNZ COMERR ;Error if file not found
XOR AX,AX
MOV [FCB+33],AX ; Set 4-byte Random Record field to
MOV [FCB+35],AX ; beginning of file.
INC AX
MOV [FCB+14],AX ;Set record length field
MOV AH,39 ;Block read (CX already set)
INT 33
JCXZ COMERR ;Error if no records read
TEST AL,1
JZ COMERR ;Error if not end-of-file
;
; Make all segment registers the same.
;
MOV DS,BX
MOV ES,BX
MOV SS,BX
MOV SP,5CH ;Set stack to standard value
XOR AX,AX
PUSH AX ;Put zero on top of stack for return
MOV DX,80H
MOV AH,26
INT 33 ;Set default transfer address (DS:0080)
PUSH BX ;Put segment on stack
MOV AX,100H
PUSH AX ;Put address to execute within segment on stack
RET L ;Jump to COMMAND
COMERR:
MOV DX,BADCOM
MOV AH,9 ;Print string
INT 33
EI
STALL: JP STALL
STCTAB: DB 17H ;Select master mode register
DW 84F3H ;Enable time-of-day
DB 1 ;Counter 1 mode register
DW 0138H
DB 2
DW 0038H
DB 3
DW 0008H ;Set counter 3 to count days
IF SERIAL
DB 0B7H, 77H, 4EH, 37H, PRNBAUD, AUXBAUD
ENDIF
BADCOM: DB 13,10,"Error in loading Command Interpreter",13,10,"$"
FCB: DB 1,"COMMAND COM"
DS 25
;
; ************ Time and Date ************
;
GETTIME:
MOV AL,0A7H ;Save counters 1,2,3
OUT STCCOM
MOV AL,0E0H ;Enable data pointer sequencing
OUT STCCOM
MOV AL,19H ;Select hold 1 / hold cycle
OUT STCCOM
CALL STCTIME ;Get seconds & 1/100's
XCHG AX,DX
CALL STCTIME ;Get hours & minutes
XCHG AX,CX
IN STCDATA
MOV AH,AL
IN STCDATA
XCHG AL,AH ;Count of days
JP POINTSTAT
STCTIME:
CALL STCBYTE
MOV CL,AH
STCBYTE:
IN STCDATA
MOV AH,AL
SHR AH
SHR AH
SHR AH
SHR AH
AND AL,0FH ;Unpack BCD digits
AAD ;Convert to binary
MOV AH,AL
MOV AL,CL
RET
SETTIME:
PUSH CX
PUSH DX
CALL LOAD0 ;Put 0 into load registers to condition timer
MOV AL,43H ;Load counters 1 & 2
OUT STCCOM
POP DX
POP CX
CALL LOAD
MOV AL,43H
OUT STCCOM ;Load counters 1&2
CALL LOAD0
MOV AL,27H ;Arm counters 1,2,3
OUT STCCOM
JP POINTSTAT
LOAD0:
XOR CX,CX
MOV DX,CX
LOAD:
MOV AL,09 ;Counter 1 load register
CALL OUTDX
MOV AL,0AH ;Counter 2 load register
MOV DX,CX
OUTDX:
OUT STCCOM ;Select a load register
MOV AL,DL
CALL OUTBCD
MOV AL,DH
OUTBCD:
AAM ;Convert binary to unpacked BCD
SHL AH
SHL AH
SHL AH
SHL AH
OR AL,AH ;Packed BCD
OUT STCDATA
RET
SETDATE:
XCHG AX,DX ;Put date in DX
MOV AL,0BH ;Select Counter 3 load register
OUT STCCOM
XCHG AX,DX
OUT STCDATA
MOV AL,AH
OUT STCDATA
MOV AL,44H ;Load counter 3
OUT STCCOM
POINTSTAT:
PUSH AX
MOV AL,1FH ;Point to status register
OUT STCCOM ; so power-off glitches won't hurt
POP AX
RET L
;
; ************ CONSOLE INPUT ************
;
IF INTINP-1 ; Non-interrupt driven input.
STATUS:
IN STAT
AND AL,DAV
JZ NOTHING ; Jump if nothing there.
PUSHF ; Save Z flag.
INB DATA
AND AL,7FH
SEG CS
MOV [QUEUE],AL ; Put new character in buffer.
POPF ; Return with Z flag clear.
RET L
NOTHING:
SEG CS
MOV AL,[QUEUE] ; See if there's anything in the buffer.
NOT AL ; Set up the Z flag.
TEST AL,80H
PUSHF
NOT AL
POPF
RET L
INP:
MOV AL,-1
SEG CS
XCHG AL,[QUEUE] ; Remove the character from the buffer.
AND AL,AL
JNS INRET ; Return if we have a character.
INLOOP:
IN STAT ; Wait till a character is available.
AND AL,DAV
JZ INLOOP
IN DATA
AND AL,7FH
INRET:
FLUSH:
RET L
QUEUE: DB -1 ; For storing characters from STATUS to INP.
ENDIF
IF INTINP ; Interrupt-driven input.
;
; Console keyboard interrupt handler.
;
KBINT:
PUSH AX
PUSH SI
MOV AL,20H ;End of Interrupt command
OUT BASE+2 ;Send to slave
IN DATA ;Get the character
AND AL,7FH
CMP AL,"C"-"@"
JZ FLSH
CMP AL,"S"-"@"
JZ FLSH
CMP AL,"F"-"@"
JNZ SAVKY
FLSH:
CALL 13*3,BIOSSEG ; Call I/O system keyboard buffer flush.
SAVKY:
SEG CS
MOV SI,[REAR] ;Pointer to rear of queue
CALL INCQ
SEG CS
CMP SI,[FRONT] ;Any room in queue?
JZ QFULL
SEG CS
MOV [SI],AL ;Put character in queue
SEG CS
MOV [REAR],SI ;Save pointer
LEAVINT:
POP SI
POP AX
IRET
QFULL:
MOV AL,7 ; BELL character.
CALL 3*3,BIOSSEG ; Call I/O system console output function.
JMPS LEAVINT
STATUS:
PUSH SI
;See if printer ready
IN PRNSTAT
AND AL,TBMT
JZ NOPRN
SEG CS
MOV SI,[PFRONT]
SEG CS
CMP SI,[PREAR] ;Anything in print queue?
JNZ SENDPRN
SEG CS
CMP B,[PRNFCB],-1 ;Print spooling in progress?
JZ NOPRN ;If not, nothing to print
;Print spooling in progress. Get next buffer
PUSH DS
PUSH CS
POP DS
PUSH AX
PUSH CX
PUSH DX
PUSH [STKSAV]
PUSH [STKSAV+2]
PUSH [DMAADD]
PUSH [DMAADD+2]
MOV DX,PQUEUE
MOV AH,26 ;Set DMA address
INT 33
MOV DX,PRNFCB
MOV CX,PBUFSIZ
MOV AH,39 ;Read buffer
INT 33
OR AL,AL
JZ NOTEOF
MOV B,[PRNFCB],-1 ;Turn off print spooling at EOF
NOTEOF:
POP [DMAADD+2]
POP [DMAADD]
POP [STKSAV+2]
POP [STKSAV]
MOV SI,CX
POP DX
POP CX
POP AX
POP DS
OR SI,SI
JZ NOPRN
ADD SI,PQUEUE-1
SEG CS
MOV [PREAR],SI
MOV SI,ENDPQ-1
SENDPRN:
CALL INCPQ
SEG CS
MOV [PFRONT],SI
SEG CS
LODSB ;Get character to print
OUT PRNDATA
NOPRN:
DI ; Disable interrupts while checking queue.
SEG CS
MOV SI,[FRONT]
SEG CS
CMP SI,[REAR] ; Anything in queue?
JZ NOCHR ; Jump if nothing in queue.
CALL INCQ
SEG CS
LODSB ;Get character (if there is one)
OR SI,SI ;Reset zero flag
NOCHR:
EI
POP SI
RET L ;Zero clear if we have a character
INP:
CALL STATUS,BIOSSEG ; Get I/O system console input status.
JZ INP
PUSH SI
DI ; Disable interrupts while changing queue pointers.
SEG CS
MOV SI,[FRONT]
CALL INCQ ; Permanently remove char from queue
SEG CS
MOV [FRONT],SI
EI
POP SI
RET L
FLUSH:
DI
SEG CS
MOV [REAR],QUEUE
SEG CS
MOV [FRONT],QUEUE
EI
RET L
INCQ:
INC SI
CMP SI,ENDQ ;Exceeded length of queue?
JB RET
MOV SI,QUEUE
RET
INCPQ:
INC SI
CMP SI,ENDPQ ;Exceeded length of queue?
JB RET
MOV SI,PQUEUE
RET
FRONT: DW QUEUE
REAR: DW QUEUE
QUEUE: DS QSIZE
ENDQ: EQU $
PFRONT: DW PQUEUE
PREAR: DW PQUEUE
PQUEUE: DS PBUFSIZ
ENDPQ: EQU $
PRNFCB: DB -1
DS 36
ENDIF
;
; ************ Console and Printer Output ************
;
OUTP:
PUSH AX
OUTLP:
IN STAT
AND AL,TBMT
JZ OUTLP
POP AX
OUT DATA
RET L
PRINT:
PUSH SI
SEG CS
MOV SI,[PREAR]
CALL INCPQ
PRINLP:
SEG CS
CMP SI,[PFRONT]
JNZ PRNCHR
;Print queue is full
PUSH AX
CALL STATUS,BIOSSEG ;Poll and maybe print something
POP AX
JMPS PRINLP
PRNCHR:
SEG CS
MOV [PREAR],SI
SEG CS
MOV [SI],AL
POP SI
RET L
;
; ************ Auxiliary I/O ************
;
AUXIN:
IN AUXSTAT
AND AL,DAV
JZ AUXIN
IN AUXDATA
RET L
AUXOUT:
PUSH AX
AUXLP:
IN AUXSTAT
AND AL,TBMT
JZ AUXLP
POP AX
OUT AUXDATA
RET L
;
; ************ 1771/1793-type controller disk I/O ************
;
TARBELL:EQU TARBELLSD+TARBELLDD
CROMEMCO:EQU CROMEMCO4FDC+CROMEMCO16FDC
WD1791: EQU SCP+TARBELLDD+CROMEMCO16FDC
WD1771: EQU TARBELLSD+CROMEMCO4FDC
IF WD1791
READCOM:EQU 80H
WRITECOM:EQU 0A0H
ENDIF
IF WD1771
READCOM:EQU 88H
WRITECOM:EQU 0A8H
ENDIF
IF SCP
SMALLBIT:EQU 10H
BACKBIT:EQU 04H
DDENBIT:EQU 08H
DONEBIT:EQU 01H
DISK: EQU 0E0H
ENDIF
IF TARBELL
BACKBIT:EQU 40H
DDENBIT:EQU 08H
DONEBIT:EQU 80H
DISK: EQU 78H
ENDIF
IF CROMEMCO
SMALLBIT:EQU 10H
BACKBIT:EQU 0FDH ; Send this to port 4 to select back.
DDENBIT:EQU 40H
DONEBIT:EQU 01H
DISK: EQU 30H
ENDIF
IF SMALLDS-1
SMALLDDSECT: EQU 8
ENDIF
IF SMALLDS
SMALLDDSECT: EQU 16
ENDIF
IF LARGEDS-1
LARGEDDSECT: EQU 8
ENDIF
IF LARGEDS
LARGEDDSECT: EQU 16
ENDIF
;
; Disk change function.
; On entry:
; AL = disk drive number.
; On exit:
; AH = -1 (FF hex) if disk is changed.
; AH = 0 if don't know.
; AH = 1 if not changed.
;
; CF clear if no disk error.
; AL = disk I/O driver number.
;
; CF set if disk error.
; AL = disk error code (see disk read below).
;
IF WD1771
DSKCHG:
MOV AH,0 ; AH = 0 in case we don't know.
SEG CS
CMP AL,[CURDRV]
JNZ RETL
PUSH AX ; Save drive number.
IF CROMEMCO
INB DISK+4
ENDIF
IF TARBELL
INB DISK
ENDIF
AND AL,20H ; Look at head load bit
POP AX
JZ RETL
MOV AH,1 ; AH = 1, disk not changed.
RETL:
CLC ; No disk error.
RET L
ENDIF ; End of 1771 DSKCHG.
IF WD1791
DSKCHG:
MOV AH,0 ; AH = 0 in case we don't know.
SEG CS
CMP AL,[CURDRV]
JNZ DENSCHK ; Check density if not same drive.
PUSH AX
IF SCP+CROMEMCO
INB DISK+4
ENDIF
IF TARBELL
INB DISK
ENDIF
AND AL,20H ; Look at head load bit
POP AX
JZ DENSCHK ; Check density if head not loaded.
MOV AH,1 ; AH = 1, disk not changed.
MOV BX,PREVDENS
SEG CS
XLAT ; Get previous density
CLC ; No disk error.
RET L
DENSCHK:
CALL CHKNEW ; Unload head if selecting new drive.
CBW
XCHG AX,SI
ADD SI,PREVDENS
MOV CX,4 ; Try each density twice
MOV AH,0 ; Disk may not have been changed.
CHKDENS:
SEG CS
MOV AL,[SI] ; Get previous disk I/O driver number.
MOV BX,DRVTAB
SEG CS
XLAT ; Get drive select byte for previous density
IF CROMEMCO16FDC
CALL MOTOR ; Wait for motor to come up to speed.
ENDIF
OUT DISK+4 ; Select disk
MOV AL,0C4H ; READ ADDRESS command
CALL DCOM
AND AL,98H
IN DISK+3 ; Eat last byte to reset DRQ
JZ HAVDENS ; Jump if no error in reading address.
NOT AH ; AH = -1 (disk changed) if new density works.
SEG CS
XOR B,[SI],1 ; Try other density
LOOP CHKDENS
MOV AX,2 ; Couldn't read disk at all, AH = 0 for don't
STC ; know if disk changed, AL = error code 2 -
RET L ; disk not ready, carry set to indicate error.
HAVDENS:
SEG CS
LODSB ; AL = disk I/O driver number.
CLC ; No disk error.
RET L
PREVDENS:DB 1,3,5,7,9,11,13 ; Table of previous disk I/O driver numbers.
ENDIF ; End of 1793 DSKCHG function.
CHKNEW:
MOV AH,AL ; Save disk drive number in AH.
SEG CS ; AL = previous disk drive number,
XCHG AL,[CURDRV] ; make new drive current.
CMP AL,AH ; Changing drives?
JZ RET
;
; If changing drives, unload head so the head load delay one-shot will
; fire again. Do it by seeking to the same track with the H bit reset.
;
IN DISK+1 ; Get current track number
OUT DISK+3 ; Make it the track to seek to
MOV AL,10H ; Seek and unload head
CALL DCOM
MOV AL,AH ; Restore current drive number
RET
IF CROMEMCO16FDC
MOTOR:
PUSH AX
MOV AH,AL
IN DISK+4 ; See if the motor is on.
TEST AL,08H
MOV AL,AH
OUTB DISK+4 ; Select drive & start motor.
JNZ MOTORSON ; No delay if motors already on.
PUSH CX
MOV CX,43716 ; Loop count for 1 second.
MOTORDELAY: ; (8 MHz, 16-bit memory).
AAM ; 83 clocks.
AAM ; 83 clocks.
LOOP MOTORDELAY ; 17 clocks.
POP CX
MOTORSON:
POP AX
RET
ENDIF
;
; Disk read function.
;
; On entry:
; AL = Disk I/O driver number
; BX = Disk transfer address in DS
; CX = Number of sectors to transfer
; DX = Logical record number of transfer
; On exit:
; CF clear if transfer complete
;
; CF set if hard disk error.
; CX = number of sectors left to transfer.
; AL = disk error code
; 0 = write protect error
; 2 = not ready error
; 4 = "data" (CRC) error
; 6 = seek error
; 8 = sector not found
; 10 = write fault
; 12 = "disk" (none of the above) error
;
READ:
CALL SEEK ;Position head
JC ERROR
PUSH ES ; Make ES same as DS.
MOV BX,DS
MOV ES,BX
RDLP:
CALL READSECT ;Perform sector read
JC POPESERROR
INC DH ;Next sector number
LOOP RDLP ;Read each sector requested
CLC ; No errors.
POP ES ; Restore ES register.
RET L
;
; Disk write function.
; Registers same on entry and exit as read above.
;
WRITE:
CALL SEEK ;Position head
JC ERROR
WRTLP:
CALL WRITESECT ;Perform sector write
JC ERROR
INC DH ;Bump sector counter
LOOP WRTLP ;Write CX sectors
CLC ; No errors.
WRITERET:
RET L
POPESERROR:
POP ES ; Restore ES register.
ERROR:
MOV BL,-1
SEG CS
MOV [DI],BL ; Indicate we don't know where head is.
MOV SI,ERRTAB
GETCOD:
INC BL ; Increment to next error code.
SEG CS
LODB
TEST AH,AL ; See if error code matches disk status.
JZ GETCOD ; Try another if not.
MOV AL,BL ; Now we've got the code.
SHL AL ; Multiply by two.
STC
RET L
ERRTAB:
DB 40H ;Write protect error
DB 80H ;Not ready error
DB 8 ;CRC error
DB 2 ;Seek error
DB 10H ;Sector not found
DB 20H ;Write fault
DB 7 ;"Disk" error
;
; Direct disk read and write from INT 37 and INT 38. Subroutine GETIODRIVER
; calls DSKCHG to convert disk drive number to I/O driver number.
;
; Setting CURDRV to -1 before calling DSKCHG forces DSKCHG to check the disk's
; density before returning the I/O driver number. This is necessary because
; programs such as FORMAT could change the density of a disk and leave the
; head loaded. If the head is loaded DSKCHG assumes the disk hasn't been
; changed and returns the old I/O driver number which could be wrong.
;
; CURDRV is set to -1 before returning so when DSKCHG is called by the
; operating system, it will tell the operating system the disk may have
; been changed (because it may have been).
;
DIRECTREAD:
IF WD1791
CALL GETIODRIVER ; Convert drive number to I/O driver number.
JC DIRECTRET ; Return if DSKCHG returned error.
ENDIF
CALL 7*3,BIOSSEG ; Call READ.
JMPS DIRECTRET
DIRECTWRITE:
IF WD1791
CALL GETIODRIVER ; Convert drive number to I/O driver number.
JC DIRECTRET ; Return if DSKCHG returned error.
ENDIF
CALL 8*3,BIOSSEG ; Call WRITE.
DIRECTRET:
SEG CS
MOV B,[CURDRV],-1 ; Force DSKCHG to do density check.
RET L
IF WD1791
GETIODRIVER:
SEG CS
MOV B,[CURDRV],-1 ; Force DSKCHG to do density check.
PUSH BX
PUSH CX
CALL 9*3,BIOSSEG ; Call DSKCHG.
POP CX
POP BX
RET
ENDIF
;
; Function:
; Seeks to proper track.
; On entry:
; Same as for disk read or write above.
; On exit:
; AH = Drive select byte
; DL = Track number
; DH = Sector number
; SI = Disk transfer address in DS
; DI = pointer to drive's track counter in CS
; CX unchanged (number of sectors)
;
SEEK:
MOV SI,BX ; Save transfer address
CBW
MOV BX,AX ; Prepare to index on drive number
IF WD1791 ; If two disk formats per drive.
SHR AL ; Convert to physical disk drive number.
ENDIF
CALL CHKNEW ; Unload head if changing drives.
SEG CS
MOV AL,[BX+DRVTAB] ; Get drive-select byte.
IF CROMEMCO16FDC
CALL MOTOR ; Wait for the motors to come up to speed.
ENDIF
OUTB DISK+4 ; Select drive.
IF CROMEMCO
OR AL,80H ; Set auto-wait bit.
ENDIF
MOV AH,AL ; Save drive-select byte in AH.
XCHG AX,DX ; AX = logical sector number.
MOV DL,26 ; 26 sectors/track unless changed below
IF SCP
TEST DH,SMALLBIT ; Check if small disk.
JZ BIGONE ; Jump if big disk.
MOV DL,18 ; Assume 18 sectors on small track.
TEST DH,DDENBIT ; Check if double-density.
JZ HAVSECT ; Jump if not.
MOV DL,SMALLDDSECT ; Number of sectors on small DD track.
JP HAVSECT
BIGONE:
TEST DH,DDENBIT ; Check if double-density.
JZ HAVSECT ; Jump if not.
MOV DL,LARGEDDSECT ; Number of sectors on big DD track.
ENDIF
IF TARBELLDD ; Tarbell DD controller.
TEST DH,DDENBIT ; Check for double-density.
JZ HAVSECT
MOV DL,LARGEDDSECT ; Number of sectors on DD track.
ENDIF
IF CROMEMCO4FDC
TEST DH,SMALLBIT ; Check if small disk.
JNZ HAVSECT ; Jump if not.
MOV DL,18 ; 18 sectors on small disk track.
ENDIF
IF CROMEMCO16FDC
TEST DH,SMALLBIT ; Check if small disk.
JNZ BIGONE ; Jump if big disk.
MOV DL,18 ; Assume 18 sectors on small track.
TEST DH,DDENBIT ; Check if double-density.
JZ HAVSECT ; Jump if not.
MOV DL,SMALLDDSECT ; Number of sectors on small DD track.
JP HAVSECT
BIGONE:
TEST DH,DDENBIT ; Check if double-density.
JZ HAVSECT ; Jump if not.
MOV DL,LARGEDDSECT ; Number of sectors on big DD track.
ENDIF
HAVSECT:
DIV AL,DL ; AL = track, AH = sector.
XCHG AX,DX ; AH has drive-select byte, DX = track & sector.
INC DH ; Sectors start at one, not zero.
SEG CS
MOV BL,[BX+TRKPT] ; Get this drive's displacement into track table.
ADD BX,TRKTAB ; BX now points to track counter for this drive.
MOV DI,BX
MOV AL,DL ; Move new track number into AL.
SEG CS
XCHG AL,[DI] ; Xchange current track with desired track
OUT DISK+1 ; Inform controller chip of current track
CMP AL,DL ; See if we're at the right track.
JZ RET
MOV BH,2 ; Seek retry count
CMP AL,-1 ; Head position known?
JNZ NOHOME ; If not, home head
TRYSK:
CALL HOME
JC SEEKERR
NOHOME:
MOV AL,DL ; AL = new track number.
OUT DISK+3
MOV AL,1CH+STPSPD ; Seek command.
CALL MOVHEAD
AND AL,98H ; Accept not ready, seek, & CRC error bits.
JZ RET
JS SEEKERR ; No retries if not ready
DEC BH
JNZ TRYSK
SEEKERR:
MOV AH,AL ; Put status in AH.
TEST AL,80H ; See if it was a Not Ready error.
STC
JNZ RET ; Status is OK for Not Ready error.
MOV AH,2 ; Everything else is seek error.
RET
SETUP:
MOV BL,DH ; Move sector number to BL to play with
IF SCP+CROMEMCO16FDC
TEST AH,DDENBIT ; Check for double density.
JZ CHECKSMALL ; Not DD, check size for SD.
ENDIF
IF TARBELLDD
TEST AH,DDENBIT ; Check for double density.
JZ CHECK26 ; Not DD.
ENDIF
IF WD1791
IF (SCP+TARBELL)*LARGEDS+SCP*SMALLDS
MOV AL,AH ; Select front side of disk.
OUT DISK+4
ENDIF
IF CROMEMCO*(LARGEDS+SMALLDS)
MOV AL,0FFH ; Select front side of disk.
OUT 04H
ENDIF
CMP BL,8 ; See if legal DD sector number.
JBE PUTSEC ; Jump if ok.
IF (LARGEDS-1)*((SMALLDS*(SCP+CROMEMCO))-1)
JP STEP ; If only SS drives, we gotta step.
ENDIF
IF SCP*LARGEDS*(SMALLDS-1)
TEST AH,SMALLBIT ; Check for 5.25 inch disk.
JNZ STEP ; Jump if small because SMALLDS is off.
ENDIF
IF SCP*SMALLDS*(LARGEDS-1)
TEST AH,SMALLBIT ; Check for 8 inch disk.
JZ STEP ; Jump if large because LARGEDS is off.
ENDIF
IF CROMEMCO16FDC*LARGEDS*(SMALLDS-1)
TEST AH,SMALLBIT ; Check for 5.25 inch disk.
JZ STEP ; Jump if small because SMALLDS is off.
ENDIF
IF CROMEMCO16FDC*SMALLDS*(LARGEDS-1)
TEST AH,SMALLBIT ; Check for 8 inch disk.
JNZ STEP ; Jump if large because LARGEDS is off.
ENDIF
IF LARGEDS+SMALLDS*(SCP+CROMEMCO)
SUB BL,8 ; Find true sector for back side.
CMP BL,8 ; See if ok now.
JA STEP ; Have to step if still too big.
IF SCP+TARBELLDD
MOV AL,AH ; Move drive select byte into AL.
OR AL,BACKBIT ; Select back side.
OUT DISK+4
ENDIF
IF CROMEMCO16FDC
MOV AL,BACKBIT ; Select back side.
OUT 04H
ENDIF
JP PUTSEC
ENDIF
ENDIF
IF SCP
CHECKSMALL:
TEST AH,SMALLBIT ; See if big disk.
JZ CHECK26 ; Jump if big.
ENDIF
IF CROMEMCO
CHECKSMALL:
TEST AH,SMALLBIT ; See if big disk.
JNZ CHECK26 ; Jump if big.
ENDIF
IF SCP+CROMEMCO
CMP BL,18 ; See if legal small SD/SS sector.
JA STEP ; Jump if not.
ENDIF
CHECK26:
CMP BL,26 ; See if legal large SD/SS sector.
JBE PUTSEC ; Jump if ok.
STEP:
INC DL ; Increment track number.
MOV AL,58H ; Step in with update.
CALL DCOM
SEG CS
INC B,[DI] ; Increment the track pointer.
MOV DH,1 ; After step, do first sector.
MOV BL,DH ; Fix temporary sector number also.
PUTSEC:
MOV AL,BL ; Output sector number to controller.
OUT DISK+2
DI ; Interrupts not allowed until I/O done
IF SCP+CROMEMCO
INB DISK+4 ; Get head-load bit.
ENDIF
IF TARBELL
INB DISK
ENDIF
NOT AL
AND AL,20H ; Check head load status
JZ RET
MOV AL,4
RET
READSECT:
CALL SETUP
MOV BL,10 ; Retry count for hard error.
XCHG DI,SI ; Transfer address to DI.
PUSH DX ; Save track & sector number.
MOV DL,DISK+3 ; Disk controller data port.
RDAGN:
OR AL,READCOM
OUT DISK
IF CROMEMCO
MOV AL,AH ; Turn on auto-wait.
OUT DISK+4
ENDIF
MOV BP,DI ; Save address for retry.
JMPS RLOOPENTRY
RLOOP:
STOB ; Write into memory.
RLOOPENTRY:
IF SCP
IN DISK+5 ; Wait for DRQ or INTRQ.
ENDIF
IF TARBELL+CROMEMCO
IN DISK+4
ENDIF
IF TARBELL
SHL AL
INB DX ; Read data from disk controller chip.
JC RLOOP
ENDIF
IF SCP+CROMEMCO
SHR AL
INB DX ; Read data from disk controller chip.
JNC RLOOP
ENDIF
EI ; Interrupts OK now
CALL GETSTAT
AND AL,9CH
JZ RDPOP
MOV DI,BP ; Get origainal address back for retry.
MOV BH,AL ; Save error status for report
MOV AL,0
DEC BL
JNZ RDAGN
MOV AH,BH ; Put error status in AH.
STC
RDPOP:
POP DX ; Get back track & sector number.
XCHG SI,DI ; Address back to SI.
IF TARBELL
FORCINT:
MOV AL,0D0H ; Tarbell controllers need this Force Interrupt
OUT DISK ; so that Type I status is always available
MOV AL,10 ; at the 1771/1793 status port so we can find
INTDLY: ; out if the head is loaded. SCP and Cromemco
DEC AL ; controllers have head-load status available
JNZ INTDLY ; at the DISK+4 status port.
ENDIF
RET
WRITESECT:
CALL SETUP
MOV BL,10
PUSH DX ; Save track & sector number.
MOV DL,DISK+3 ; Disk controller data port.
WRTAGN:
OR AL,WRITECOM
OUT DISK
IF CROMEMCO
MOV AL,AH ; Turn on auto-wait.
OUT DISK+4
ENDIF
MOV BP,SI
WRLOOP:
IF SCP
INB DISK+5
ENDIF
IF TARBELL+CROMEMCO
INB DISK+4
ENDIF
IF SCP+CROMEMCO
SHR AL
LODB ; Get data from memory.
OUTB DX ; Write to disk.
JNC WRLOOP
ENDIF
IF TARBELL
SHL AL
LODB ; Get data from memory.
OUTB DX ; Write to disk.
JC WRLOOP
ENDIF
EI ; Interrupts OK now.
DEC SI
CALL GETSTAT
AND AL,0FCH
JZ WRPOP
MOV SI,BP
MOV BH,AL
MOV AL,0
DEC BL
JNZ WRTAGN
MOV AH,BH ; Error status to AH.
STC
WRPOP:
POP DX ; Get back track & sector number.
IF TARBELL
JMPS FORCINT
ENDIF
IF SCP+CROMEMCO
RET
ENDIF
;
; Subroutine to restore the read/write head to track 0.
;
IF SCP+CROMEMCO+TARBELL*(FASTSEEK-1)
HOME:
ENDIF
IF FASTSEEK*CROMEMCO
TEST AH,SMALLBIT ; Check for large disk.
JNZ RESTORE ; Big disks are fast seek PerSci.
ENDIF
MOV BL,3
TRYHOM:
IF SCP*FASTSEEK
MOV AL,AH ; Turn on Restore to PerSci.
OR AL,80H
OUTB DISK+4
ENDIF
MOV AL,0CH+STPSPD ; Restore with verify command.
CALL DCOM
AND AL,98H
IF SCP*FASTSEEK
MOV AL,AH ; Restore off.
OUTB DISK+4
ENDIF
JZ RET
JS HOMERR ; No retries if not ready
MOV AL,58H+STPSPD ; Step in with update
CALL DCOM
DEC BL
JNZ TRYHOM
HOMERR:
STC
RET
;
; RESTORE for PerSci drives.
; Doesn't exist yet for Tarbell controllers.
;
IF FASTSEEK*TARBELL
HOME:
RESTORE:
RET
ENDIF
IF FASTSEEK*CROMEMCO4FDC
RESTORE:
MOV AL,0C4H ;READ ADDRESS command to keep head loaded
OUT DISK
MOV AL,77H
OUT 4
CHKRES:
IN 4
AND AL,40H
JZ RESDONE
IN DISK+4
TEST AL,DONEBIT
JZ CHKRES
IN DISK
JP RESTORE ;Reload head
RESDONE:
MOV AL,7FH
OUT 4
CALL GETSTAT
MOV AL,0
OUT DISK+1 ;Tell 1771 we're now on track 0
RET
ENDIF
IF FASTSEEK*CROMEMCO16FDC
RESTORE:
MOV AL,0D7H ; Turn on Drive-Select and Restore.
OUTB 4
PUSH AX
AAM ; 10 uS delay.
POP AX
RESWAIT:
INB 4 ; Wait till Seek Complete is active.
TEST AL,40H
JNZ RESWAIT
MOV AL,0FFH ; Turn off Drive-Select and Restore.
OUTB 4
SUB AL,AL ; Tell 1793 we're on track 0.
OUTB DISK+1
RET
ENDIF
;
; Subroutine to move the read/write head to the desired track.
; Usually falls through to DCOM unless special handling for
; PerSci drives is required in which case go to FASTSK.
;
IF SCP+CROMEMCO+TARBELL*(FASTSEEK-1)
MOVHEAD:
ENDIF
IF CROMEMCO*FASTSEEK
TEST AH,SMALLBIT ; Check for PerSci.
JNZ FASTSK
ENDIF
DCOM:
OUT DISK
PUSH AX
AAM ;Delay 10 microseconds
POP AX
GETSTAT:
IN DISK+4
TEST AL,DONEBIT
IF TARBELL
JNZ GETSTAT
ENDIF
IF SCP+CROMEMCO
JZ GETSTAT
ENDIF
IN DISK
RET
;
; Fast seek code for PerSci drives.
; Tarbell not installed yet.
;
IF FASTSEEK*TARBELL
MOVHEAD:
FASTSK:
RET
ENDIF
IF FASTSEEK*CROMEMCO
FASTSK:
MOV AL,6FH
OUT 4
MOV AL,18H
CALL DCOM
SKWAIT:
IN 4
TEST AL,40H
JNZ SKWAIT
MOV AL,7FH
OUT 4
MOV AL,0
RET
ENDIF
CURDRV: DB -1
;
; Explanation of tables below.
;
; DRVTAB is a table of bytes which are sent to the disk controller as drive-
; select bytes to choose which physical drive is selected for each disk I/O
; driver. It also selects whether the disk is 5.25-inch or 8-inch, single-
; density or double-density. Always select side 0 in the drive-select byte if
; a side-select bit is available. There should be one entry in the DRVTAB
; table for each disk I/O driver. Exactly which bits in the drive-select byte
; do what depends on which disk controller is used.
;
; TRKTAB is a table of bytes used to store which track the read/write
; head of each drive is on. Each physical drive should have its own
; entry in TRKTAB.
;
; TRKPT is a table of bytes which indicates which TRKTAB entry each
; disk I/O driver should use. Since each physical drive may be used for
; more than one disk I/O driver, more than one entry in TRKPT may point
; to the same entry in TRKTAB. Drives such as PerSci 277s which use
; the same head positioner for more than one drive should share entrys
; in TRKTAB.
;
; INITTAB is the initialization table for 86-DOS as described in the
; 86-DOS Programer's Manual under "Customizing the I/O System."
;
IF SCP*COMBIN*FASTSEEK
;
; A PerSci 277 or 299 and one 5.25-inch drive.
;
DRVTAB: DB 00H,08H,01H,09H,10H,18H,00H,08H,01H,09H
TRKPT: DB 0,0,0,0,1,1,0,0,0,0
TRKTAB: DB -1,-1
INITTAB:
IF CONVERT-1
DB 6 ; Number of disk I/O drivers.
ENDIF
IF CONVERT
DB 10
ENDIF
DB 0 ; Disk I/O driver 0 uses disk drive 0.
DW LSDRIVE ; Disk I/O driver 0 is 8-inch single-density.
DB 0 ; Disk I/O driver 1 uses disk drive 0.
DW LDDRIVE ; Disk I/O driver 1 is 8-inch double-density.
DB 1 ; Etc.
DW LSDRIVE
DB 1
DW LDDRIVE
DB 2
DW SSDRIVE
DB 2
DW SDDRIVE
IF CONVERT
DB 3
DW OLDLSDRIVE
DB 3
DW OLDLDDRIVE
DB 4
DW OLDLSDRIVE
DB 4
DW OLDLDDRIVE
ENDIF
ENDIF
IF SCP*LARGE*FASTSEEK
;
; PerSci 277 or 299.
;
DRVTAB: DB 00H,08H,01H,09H,00H,08H,01H,09H
TRKPT: DB 0,0,0,0,0,0,0,0
TRKTAB: DB -1
INITTAB:
IF CONVERT-1
DB 4
ENDIF
IF CONVERT
DB 8
ENDIF
DB 0
DW LSDRIVE
DB 0
DW LDDRIVE
DB 1
DW LSDRIVE
DB 1
DW LDDRIVE
IF CONVERT
DB 2
DW OLDLSDRIVE
DB 2
DW OLDLDDRIVE
DB 3
DW OLDLSDRIVE
DB 3
DW OLDLDDRIVE
ENDIF
ENDIF
IF TARBELLDD
;
; Two 8-inch Shugart-type drives.
;
DRVTAB: DB 0,8,10H,18H,0,8,10H,18H
TRKPT: DB 0,0,1,1,0,0,1,1
TRKTAB: DB -1,-1
INITTAB:
IF CONVERT-1
DB 4
ENDIF
IF CONVERT
DB 8
ENDIF
DB 0
DW LSDRIVE
DB 0
DW LDDRIVE
DB 1
DW LSDRIVE
DB 1
DW LDDRIVE
IF CONVERT
DB 2
DW OLDLSDRIVE
DB 2
DW OLDLDDRIVE
DB 3
DW OLDLSDRIVE
DB 3
DW OLDLDDRIVE
ENDIF
ENDIF
IF TARBELLSD
;
; Four 8-inch Shugart-type drives.
;
DRVTAB: DB 0F2H,0E2H,0F2H,0E2H
TRKPT: DB 0,1,0,1
TRKTAB: DB -1,-1
INITTAB:
IF CONVERT-1
DB 2
ENDIF
IF CONVERT
DB 4
ENDIF
DB 0
DW LSDRIVE
DB 1
DW LSDRIVE
IF CONVERT
DB 2
DW OLDLSDRIVE
DB 3
DW OLDLSDRIVE
ENDIF
ENDIF
;
; Cromemco drive select byte is derived as follows:
; Bit 7 = 0
; Bit 6 = 1 if double density (if 16FDC)
; Bit 5 = 1 (motor on)
; Bit 4 = 0 for 5", 1 for 8" drives
; Bit 3 = 1 for drive 3
; Bit 2 = 1 for drive 2
; Bit 1 = 1 for drive 1
; Bit 0 = 1 for drive 0
;
IF CROMEMCO4FDC*LARGE
;
; PerSci 277 drive.
;
DRVTAB: DB 31H,32H,31H,32H
TRKPT: DB 0,0,0,0
TRKTAB: DB -1
INITTAB:
IF CONVERT-1
DB 2
ENDIF
IF CONVERT
DB 4
ENDIF
DB 0
DW LSDRIVE
DB 1
DW LSDRIVE
IF CONVERT
DB 2
DW OLDLSDRIVE
DB 3
DW OLDLSDRIVE
ENDIF
ENDIF
IF CROMEMCO4FDC*COMBIN
;
; A PerSci 277 and one 5.25-inch drive.
;
DRVTAB: DB 31H,32H,24H,31H,32H
TRKPT: DB 0,0,1,0,0
TRKTAB: DB -1,-1
INITTAB:
IF CONVERT-1
DB 3
ENDIF
IF CONVERT
DB 5
ENDIF
DB 0
DW LSDRIVE
DB 1
DW LSDRIVE
DB 2
DW SSDRIVE
IF CONVERT
DB 3
DW OLDLSDRIVE
DB 4
DW OLDLSDRIVE
ENDIF
ENDIF
IF CROMEMCO4FDC*SMALL
;
; Three 5.25-inch drives.
;
DRVTAB: DB 21H,22H,24H
TRKPT: DB 0,1,2
TRKTAB: DB -1,-1,-1
INITTAB:DB 3
DB 0
DW SSDRIVE
DB 1
DW SSDRIVE
DB 2
DW SSDRIVE
ENDIF
IF CUSTOM
;
; Cromemco 4FDC with two 8-inch Shugart-type drives.
;
DRVTAB: DB 31H,32H,31H,32H
TRKPT: DB 0,1,0,1
TRKTAB: DB -1,-1
INITTAB:
IF CONVERT-1
DB 2
ENDIF
IF CONVERT
DB 4
ENDIF
DB 0
DW LSDRIVE
DB 1
DW LSDRIVE
IF CONVERT
DB 2
DW OLDLSDRIVE
DB 3
DW OLDLSDRIVE
ENDIF
ENDIF
IF CROMEMCO16FDC*SMALL
;
; Three 5.25-inch drives.
;
DRVTAB: DB 21H,61H,22H,62H,24H,64H
TRKPT: DB 0,0,1,1,2,2
TRKTAB: DB -1,-1,-1
INITTAB:DB 6
DB 0
DW SSDRIVE
DB 0
DW SDDRIVE
DB 1
DW SSDRIVE
DB 1
DW SDDRIVE
DB 2
DW SSDRIVE
DB 2
DW SDDRIVE
ENDIF
IF CROMEMCO16FDC*COMBIN
;
; A PerSci 277 or 299 and one 5.25-inch drive.
;
DRVTAB: DB 31H,71H,32H,72H,24H,64H,31H,71H,32H,72H
TRKPT: DB 0,0,0,0,1,1,0,0,0,0
TRKTAB: DB -1,-1
INITTAB:
IF CONVERT-1
DB 6
ENDIF
IF CONVERT
DB 10
ENDIF
DB 0
DW LSDRIVE
DB 0
DW LDDRIVE
DB 1
DW LSDRIVE
DB 1
DW LDDRIVE
DB 2
DW SSDRIVE
DB 2
DW SDDRIVE
IF CONVERT
DB 3
DW OLDLSDRIVE
DB 3
DW OLDLDDRIVE
DB 4
DW OLDLSDRIVE
DB 4
DW OLDLDDRIVE
ENDIF
ENDIF
IF CROMEMCO16FDC*LARGE
;
; A PerSci 277 or 299.
;
DRVTAB: DB 31H,71H,32H,72H,31H,71H,32H,72H
TRKPT: DB 0,0,0,0,0,0,0,0
TRKTAB: DB -1
INITTAB:
IF CONVERT-1
DB 4
ENDIF
IF CONVERT
DB 8
ENDIF
DB 0
DW LSDRIVE
DB 0
DW LDDRIVE
DB 1
DW LSDRIVE
DB 1
DW LDDRIVE
IF CONVERT
DB 2
DW OLDLSDRIVE
DB 2
DW OLDLDDRIVE
DB 3
DW OLDLSDRIVE
DB 3
DW OLDLDDRIVE
ENDIF
ENDIF
IF SMALL+COMBIN
SSDRIVE:
DW 128 ; Sector size in bytes.
DB 2 ; Sector per allocation unit.
DW 54 ; Reserved sectors.
DB 2 ; Number of allocation tables.
DW 64 ; Number of directory entrys.
DW 720 ; Number of sectors on the disk.
IF SMALLDS-1
SDDRIVE: ; This is the IBM Personal Computer
DW 512 ; disk format.
DB 1
DW 1
DB 2
DW 64
DW 320
ENDIF
IF SMALLDS
SDDRIVE:
DW 512
DB 2
DW 1
DB 2
DW 112
DW 640
ENDIF
ENDIF ; End of small drive DPTs.
IF COMBIN+LARGE
LSDRIVE:
DW 128 ; Size of sector in bytes.
DB 4 ; Sectors per allocation unit.
DW 1 ; Number of reserved sectors.
DB 2 ; Number of File Allocation Tables.
DW 68 ; Number of directory entrys.
DW 77*26 ; Number of sectors on the disk.
IF CONVERT
OLDLSDRIVE:
DW 128
DB 4
DW 52 ; Old format had two tracks reserved.
DB 2
DW 64 ; 64 directory entrys.
DW 77*26
ENDIF
IF LARGEDS-1
OLDLDDRIVE:
LDDRIVE:
DW 1024
DB 1
DW 1
DB 2
DW 96
DW 77*8
ENDIF
IF LARGEDS
LDDRIVE:
DW 1024
DB 1
DW 1
DB 2
DW 192 ; 192 directory entrys in new 8-inch DD/DS format.
DW 77*8*2
IF CONVERT
OLDLDDRIVE:
DW 1024
DB 1
DW 1
DB 2
DW 128 ; 128 directory entrys in old 8-inch DD/DS format.
DW 77*8*2
ENDIF
ENDIF
ENDIF ; End of large drive DPTs.
DOSSEG: EQU ($+15)/16+BIOSSEG ; Compute segment to use for 86-DOS.
DOSDIF: EQU 16*(DOSSEG-BIOSSEG)
STKSAV: EQU 1701H+DOSDIF
DMAADD: EQU 15B4H+DOSDIF
END

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