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erkyrath.infocom-zcode-terps/apple/zip/rwts.asm
Andrew Plotkin b642da811e Initial commit.
2023-11-16 18:19:54 -05:00

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PAGE
SBTTL "--- BOOT CODE & RWTS: APPLE II ---"
; ---------
; BOOT CODE
; ---------
; LOADS ALL OF TRACK 0 INTO RAM AT $800 TO $1800,
; THEN JUMPS THROUGH [COLD]
ORG ZIP
DB $01 ; MAGICAL MYSTERY BYTE
; BOOT BEGINS HERE
BOOT: LDA BADDR+HI ; CHECK MSB OF BOOT ADDRESS
CMP #$09 ; 1ST ENTRY INTO BOOT?
BNE BT0 ; NO, CONTINUE
; CALC ADDRESS OF ROM SECTOR READ ROUTINE
LDA BSLOT ; GET SLOT ID * 16
STA DCBSLT ; MAKE IT THE DEFAULT TARGET
STA DCBPSL ; AND THE "OLD" SLOT
LSR A ; DIVIDE BY 16
LSR A
LSR A
LSR A
ORA #%11000000 ; MAKE IT $C0nn
STA I+HI ; USE AS MSB OF ADDRESS
LDA #$5C ; LSB IS ALWAYS $5C
STA I+LO
LDA #1
STA DCBSEC
BT0: LDX DCBSEC
INC DCBSEC
CPX #$10
BCS BT1
LDA ILEAVE,X
STA BSECT
LDX BSLOT
JMP (I)
BT1: JSR INIT
JMP COLD ; LOAD REMAINDER OF ZIP
; ---------------------
; SECTOR INTERLEAVE MAP
; ---------------------
; USED BY "BOOT" AND "RWTS"
; MUST BE IN 1ST PAGE!
ILEAVE: DB $00,$04,$08,$0C,$01,$05,$09,$0D
DB $02,$06,$0A,$0E,$03,$07,$0B,$0F
; INFOCOM'S VERSION OF APPLE RWTS (READ/WRITE TRACK/SECTOR)
; HACKED BY ANDREW KALUZNIACKI
; FROM THE DOS RWTS ON APPLE DOS 3.3
; ------------
; SPACE FILLER
; ------------
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00,$00,$00,$00,$00,$00
DB $00,$00,$00
; -------------------------------
; MAIN ENTRY INTO INFO-DOS (IDOS)
; -------------------------------
; [DCBSEC] SECTOR (0-15), SET BY CALLER
; [DCBTRK] TRACK (0-34), SET BY CALLER
; [DCBDRV] DRIVE (1 OR 2), SET BY CALLER [BOOT DEFAULT]
; [DCBSLT] SLOT*16, SET BY CALLER [BOOT DEFAULT]
; [DCBPSL] SLOT*16 OF LAST USED SLOT, SET BY BOOT
; [DCBPDR] LAST DRIVE USED (1 OR 2), SET BY BOOT
; [DCBCMD] STORAGE FOR COMMAND SENT IN <A> AT CALL TO IDOS
; [DCBERR] IDOS ERROR CODE
; [DCBBFL] DISK BUFFER ADDRESS (LSB) [BOOT = IOBUFF]
; [DCBBFH] DISK BUFFER ADDRESS (MSB) [BOOT = IOBUFF]
; <A>=1 WRITES DISK BUFFER
; <A>=0 READS DISK BUFFER
; [IOBUFF] = 256-BYTE BUFFER FOR DISK I/O
; (OPTIONAL IF [DCBBFL/DCBBFH] ARE SET)
; [BUFFA] ONE PAGE BUFFER
; [BUFFB] $56 BYTE BUFFER
; CARRY CLEAR ON RETURN IF NO ERROR
; IF CARRY SET, ERROR CODE IS IN [DERR]:
; $10 = WRITE PROTECTED
; $40 = DRIVE ERROR
; $80 = READ ERROR
; *** WARNING ***
; IDOS MUST START ON A PAGE BOUNDARY.
; CHANGE ANY CODE BETWEEN [IDOS] AND [INIT] AT YOUR OWN RISK.
; YOU HAVE BEEN WARNED.
IDOS: NOP
NOP
NOP ; DON'T ASK, AND DON'T CHANGE
PHP ; SAVE STATUS OF [I]
SEI ; DISABLE INTERUPTS
JSR DOS ; DO IT (GO TO MAIN ROUTINE)
BCS DOSERR ; ERROR OCCURED IF C=1
PLP ; RESTORE [I]
CLC ; SET "NO ERROR"
RTS ; RETURN FROM CALL
DOSERR: PLP ; RESTORE [I]
SEC ; INDICATE ERROR
RTS ; EXIT
; PRE-NIBBLIZE [IOBUFF] BEFORE WRITING
PRENIB: LDX #0
LDY #2
PREN0: DEY
LDA (DCBBFL),Y
LSR A
ROL BUFFB,X
LSR A
ROL BUFFB,X
STA BUFFA,Y
INX
CPX #$56
BCC PREN0
LDX #0
TYA
BNE PREN0
LDX #$55 ; CLEAR BITS 7 AND 6
PREN1: LDA BUFFB,X ; OF TOP NIBBLE BUFFER
AND #%00111111
STA BUFFB,X
DEX
BPL PREN1
RTS
; ------------
; WRITE SECTOR
; ------------
; WRITES PRENIBBLIZED DATA AT [BUFFA/BUFFB] TO DISK
; ENTRY: SLOT*16 IN [X]
; EXIT: CARRY SET IF ERROR
WRTDTA: STX DTMP4 ; SAVE SLOT ID HERE
STX SLTMP2
SEC ; SET CARRY FOR POSSIBLE ERROR
LDA Q6H,X ; CHECK FOR WRITE-PROTECT
LDA Q7L,X
BMI WRT5 ; EXIT W/CARRY SET IF PROTECTED
LDA BUFFB ; SAVE 1ST BYTE OF 2NDARY BUFFER
STA DTMP3 ; FOR LATER
LDA #$FF ; ESTABLISH AUTOSYNC BYTE
STA Q7H,X ; SET DRIVE TO WRITE MODE
ORA Q6L,X ; WAIT FOR HARDWARE TO SETTLE
PHA
PLA
NOP
LDY #4 ; WRITE 5 AUTOSYNC BYTES
WRT1: PHA
PLA
JSR WRBYT2 ; USING 40 uS DELAY
DEY
BNE WRT1
LDA #$D5 ; WRITE DATA FIELD PROLOGUE:
JSR WRBYT1 ; $D5-$AA-$AD
LDA #$AA
JSR WRBYT1
LDA #$AD
JSR WRBYT1
TYA ; A BRIEF DELAY
LDY #$56 ; INIT LOOP INDEX
BNE WRT3 ; BRANCH ALWAYS
; WRITE [BUFFB] TO DISK
WRT2: LDA BUFFB,Y ; GET A BYTE FROM [BUFFB]
WRT3: EOR BUFFB-1,Y
TAX ; USE IT AS AN INDEX
LDA WRTTBL,X ; INTO THE TRANSLATE TABLE
LDX DTMP4 ; RESTORE SLOT ID
STA Q6H,X ; AND WRITE THE TRANSLATED BYTE
LDA Q6L,X
DEY ; LOOP TILL
BNE WRT2 ; EMPTY
; WRITE [BUFFA] TO DISK
LDA DTMP3 ; RESTORE "LOST" [BUFFB] BYTE
NOP ; WAIT JUST A MOMENT ...
WRT4: EOR BUFFA,Y ; GET A BYTE FROM [BUFFA]
TAX ; USE IT AS AN INDEX
LDA WRTTBL,X ; INTO THE TRANSLATE TABLE
LDX SLTMP2 ; RESTORE SLOT ID
STA Q6H,X ; AND WRITE THE TRANSLATED BYTE
LDA Q6L,X
LDA BUFFA,Y ; GET NEXT BYTE FROM BUFFER
INY ; AND LOOP TILL
BNE WRT4 ; ALL OF [BUFFA] IS WRITTEN
TAX
LDA WRTTBL,X
LDX DTMP4 ; RESTORE SLOT ID
JSR WRBYT3 ; AND WRITE THE LAST [BUFFA] BYTE
LDA #$DE ; WRITE DATA FIELD EPILOGUE:
JSR WRBYT1 ; $DE-$AA-$EB
LDA #$AA
JSR WRBYT1
LDA #$EB
JSR WRBYT1
LDA #$FF ; WRITE GAP 3
JSR WRBYT1
LDA Q7L,X ; SET DRIVE TO READ MODE
WRT5: LDA Q6L,X
RTS
; ----------------------------
; WRITE A BYTE (TIME-CRITICAL)
; ----------------------------
; ENTRY: BYTE TO WRITE IN [A]
; SLOT*16 IN [X]
WRBYT1: CLC ; PROLOGUE, EPILOGUE AND GAP 3 TIMING
WRBYT2: PHA ; ENTRY FOR GAP 2 TIMING
PLA
WRBYT3: STA Q6H,X
ORA Q6L,X
RTS
; CONVERT RAW DATA TO BINARY IN [IOBUFF]
POSTNB: LDY #0
PST0: LDX #$56
PST1: DEX
BMI PST0
LDA BUFFA,Y
LSR BUFFB,X
ROL A
LSR BUFFB,X
ROL A
STA (DCBBFL),Y
INY
CPY DTMP3
BNE PST1
RTS
; -----------
; READ SECTOR
; -----------
; READ RAW SECTOR DATA TO [BUFFA/BUFFB]
; ENTRY: SLOT*16 IN [X]
; EXIT: CARRY SET IF ERROR, ELSE 342 RAW BYTES IN [BUFFA/BUFFB]
RDSECT: LDY #$20
RDS1: DEY ; RETURN AN ERROR IF
BEQ RDBAD ; NO $D5 FOUND AFTER 32 TRIES
; FETCH & VALIDATE PROLOGUE ($D5-$AA-$AD)
RDS2: LDA Q6L,X ; GET A BYTE
BPL RDS2
RDS3: EOR #$D5 ; WAS IT $D5?
BNE RDS1 ; NO, KEEP LOOKING
NOP ; ELSE WAIT A MOMENT ...
RDS4: LDA Q6L,X ; GET ANOTHER BYTE
BPL RDS4
CMP #$AA ; WAS IT $AA?
BNE RDS3 ; CHECK FOR $D5 AGAIN IF NOT
LDY #$56 ; ELSE INIT DATA-READ INDEX
RDS5: LDA Q6L,X ; GET A BYTE
BPL RDS5
CMP #$AD ; WAS IT $AD?
BNE RDS3 ; CHECK FOR $D5 IF NOT
; READ RAW DATA INTO [BUFFB]
LDA #0 ; CLEAR [A], DELAY ...
RDS6: DEY
STY DTMP3 ; SAVE INDEX HERE
RDS7: LDY Q6L,X ; GET A DATA BYTE
BPL RDS7
EOR RDTBL-$96,Y ; TRANSLATE IT
LDY DTMP3 ; RESTORE INDEX
STA BUFFB,Y ; STORE BYTE IN [BUFFB]
BNE RDS6 ; CONTINUE TILL [BUFFB] FULL
; READ RAW DATA INTO [BUFFA]
RDS8: STY DTMP3 ; RE-INIT INDEX TO ZERO
RDS9: LDY Q6L,X ; GET A DATA BYTE
BPL RDS9
EOR RDTBL-$96,Y ; TRANSLATE IT
LDY DTMP3 ; RESTORE INDEX
STA BUFFA,Y ; SAVE BYTE IN [BUFFA]
INY
BNE RDS8 ; LOOP TILL [BUFFA] IS FULL
; FETCH & VALIDATE CHECKSUM
RDS10: LDY Q6L,X ; GET THE NEXT BYTE
BPL RDS10
CMP RDTBL-$96,Y ; TRANSLATE IT
BNE RDBAD ; ERROR IF CHECKSUM BAD
; FETCH & VALIDATE EPILOGUE ($DE-$AA-$EB)
RDS11: LDA Q6L,X ; GET A BYTE
BPL RDS11
CMP #$DE ; IS IT $DE?
BNE RDBAD ; ERROR IF NOT
NOP ; WAIT ...
RDS12: LDA Q6L,X ; GET ANOTHER BYTE
BPL RDS12
CMP #$AA ; IS IT $AA?
BEQ RDOK ; DATA OKAY IF SO
RDBAD: SEC ; ELSE SET CARRY FOR ERROR
RTS ; AND SCRAM
; ---------------------
; READ AN ADDRESS FIELD
; ---------------------
; ENTRY: SLOT*16 IN [X]
; EXIT: CARRY SET IF ERROR
RDADDR: LDY #$FC ; INIT TIMEOUT COUNTER
STY DTMP3
RDA1: INY
BNE RDA2
INC DTMP3 ; ERROR IF
BEQ RDBAD ; CAN'T FIND ADDRESS HEADER
; FETCH THE ADDRESS FIELD PROLOGUE ($D5-$AA-$96)
RDA2: LDA Q6L,X ; GRAB A BYTE
BPL RDA2
RDA3: CMP #$D5 ; WAS IT $D5?
BNE RDA1 ; NO, KEEP SEARCHING
NOP ; ELSE WAIT A FEW MICROSECONDS ...
RDA4: LDA Q6L,X ; GET ANOTHER BYTE
BPL RDA4
CMP #$AA ; WAS IT $AA?
BNE RDA3 ; NO, CHECK IF $D5
LDY #3 ; ELSE INIT DATA-FETCH INDEX
RDA5: LDA Q6L,X ; GET A BYTE
BPL RDA5
CMP #$96 ; WAS IT $96?
BNE RDA3 ; NO, CHECK FOR $D5
; FETCH THE 4 BYTES OF ADDRESS DATA
LDA #0 ; INIT CHECKSUM BYTE
RDA6: STA DTMP4 ; UPDATE CHECKSUM
RDA7: LDA Q6L,X ; GET A BYTE
BPL RDA7
ROL A ; SHIFT IT
STA DTMP3 ; AND SAVE 1ST PART HERE
RDA8: LDA Q6L,X ; GET ANOTHER BYTE
BPL RDA8
AND DTMP3 ; SUPER 1ST PART OF BYTE
STA HDRCHK,Y ; STORE IN RESULT TABLE
EOR DTMP4 ; COMPUTE CHECKSUM
DEY ; GOT 4 BYTES YET?
BPL RDA6 ; NO, LOOP BACK
TAY ; LOOK AT CHECKSUM BYTE
BNE RDBAD ; ERROR IF NON-ZERO
; FETCH & VALIDATE EPILOGUE ($DE-$AA, IGNORE $EB)
RDA9: LDA Q6L,X ; GET A BYTE
BPL RDA9
CMP #$DE ; WAS IT $DE?
BNE RDBAD ; ERROR IF NOT
NOP ; ELSE WAIT A MOMENT ...
RDA10: LDA Q6L,X ; GET ONE MORE BYTE
BPL RDA10
CMP #$AA ; WAS IT $AA
BNE RDBAD ; ERROR IF NOT
RDOK: CLC ; ELSE CLEAR CARRY FOR SUCCESS
RTS ; AND RETURN
; ---------------------
; MOVE ARM TO TRACK [A]
; ---------------------
; ENTRY: SLOT*16 IN [X]
; TARGET TRACK IN [A]
; CURRENT TRACK IN [CTRACK]
SEEK: STX SLTMP3 ; SAVE SLOT ID
STA TTRK ; AND TARGET TRACK
CMP CTRACK ; TARGET SAME AS CURRENT?
BEQ SEEKEX ; EXIT NOW IF SO
LDA #0 ; INIT
STA DTMP3 ; INDEX
SK1: LDA CTRACK ; GET CURRENT TRACK
STA DTMP4 ; SAVE IT HERE
SEC
SBC TTRK ; GET TRACK DIFFERENCE
BEQ SK6
BCS SK2
EOR #%11111111
INC CTRACK
BCC SK3
SK2: ADC #$FE
DEC CTRACK
SK3: CMP DTMP3
BCC SK4
LDA DTMP3
SK4: CMP #$0C
BCS SK5
TAY
SK5: SEC
JSR SEEK0
LDA DELTB1,Y
JSR ARMDEL
LDA DTMP4
CLC
JSR SEEK1
LDA DELTB2,Y
JSR ARMDEL
INC DTMP3
BNE SK1
SK6: JSR ARMDEL
CLC
SEEK0: LDA CTRACK
SEEK1: AND #%00000011
ROL A
ORA SLTMP3
TAX
LDA PH0OFF,X ; MOVE THE ARM
LDX SLTMP3
SEEKEX: RTS
; ------------------
; ARM MOVEMENT DELAY
; ------------------
; NOTE: THIS ROUTINE MUST BEGIN ON A PAGE BOUNDARY!
; ENTRY: 100uS DELAY INTERVAL IN [A]
; MOTOR TIME COUNT IN [MTIME]
ARMDEL: LDX #$11
ARM1: DEX
BNE ARM1
INC DCNT
BNE ARM2
INC DTMP2
ARM2: SEC
SBC #1
BNE ARMDEL
RTS
; -------------------------
; ARM MOVEMENT DELAY TABLES
; -------------------------
DELTB1: DB $01,$30,$28,$24,$20,$1E,$1D,$1C
DB $1C,$1C,$1C,$1C
DELTB2: DB $70,$2C,$26,$22,$1F,$1E,$1D,$1C
DB $1C,$1C,$1C,$1C
; ---------------------
; WRITE TRANSLATE TABLE
; ---------------------
WRTTBL: DB $96,$97,$9A,$9B,$9D,$9E,$9F,$A6
DB $A7,$AB,$AC,$AD,$AE,$AF,$B2,$B3
DB $B4,$B5,$B6,$B7,$B9,$BA,$BB,$BC
DB $BD,$BE,$BF,$CB,$CD,$CE,$CF,$D3
DB $D6,$D7,$D9,$DA,$DB,$DC,$DD,$DE
DB $DF,$E5,$E6,$E7,$E9,$EA,$EB,$EC
DB $ED,$EE,$EF,$F2,$F3,$F4,$F5,$F6
DB $F7,$F9,$FA,$FB,$FC,$FD,$FE,$FF
; --------------------
; READ TRANSLATE TABLE
; --------------------
RDTBL: DB $00,$01,$98,$99,$02,$03,$9C,$04
DB $05,$06,$A0,$A1,$A2,$A3,$A4,$A5
DB $07,$08,$A8,$A9,$AA,$09,$0A,$0B
DB $0C,$0D,$B0,$B1,$0E,$0F,$10,$11
DB $12,$13,$B8,$14,$15,$16,$17,$18
DB $19,$1A,$C0,$C1,$C2,$C3,$C4,$C5
DB $C6,$C7,$C8,$C9,$CA,$1B,$CC,$1C
DB $1D,$1E,$D0,$D1,$D2,$1F,$D4,$D5
DB $20,$21,$D8,$22,$23,$24,$25,$26
DB $27,$28,$E0,$E1,$E2,$E3,$E4,$29
DB $2A,$2B,$E8,$2C,$2D,$2E,$2F,$30
DB $31,$32,$F0,$F1,$33,$34,$35,$36
DB $37,$38,$F8,$39,$3A,$3B,$3C,$3D
DB $3E,$3F
; ---------------
; MAIN RWTS ENTRY
; ---------------
; ENTRY: [A]=0 FOR READ, [A]=1 FOR WRITE
; [SLOT] = TARGET SLOT
; [DRIVE] = TARGET DRIVE
; [TRACK] = TARGET TRACK
; [SECTOR] = TARGET SECTOR
; EXIT: CARRY CLEAR IF OKAY
; COMMENTS - LINDE
; ACTUAL VARIABLES ARE:
; [DCBSLT] = SLOT
; [DCBTRK] = TRACK
; [DCBSEC] = SECTOR
; [[DCBDRV] = DRIVE
; FOR TRK, SEC, DRV 1 = 1 (DRIVE 1, SET DCBDRV TO 1)
; FOR SLT - MULTIPLY SLOT BY 16 (SLOT 6, SET DCBSLT TO $60)
DOS: STA DCBCMD ; SAVE COMMAND
LDA #2 ; ALLOW 2
STA NRECAL ; RECALS
ASL A ; AND 4
STA NSEEK ; SEEKS
LDX DCBSLT ; GET REQUESTED SLOT ID
CPX DCBPSL ; SAME AS LAST SLOT?
BEQ SAMESL ; YES, CONTINUE
LDX DCBPSL
; WAIT FOR OLD DRIVE TO TURN OFF, UPDATE SLOT ID
LDA Q7L,X ; SET OLD SLOT TO READ MODE
RW1: LDY #8 ; INIT COUNTER
LDA Q6L,X
RW2: CMP Q6L,X
BNE RW1
DEY
BNE RW2
LDX DCBSLT ; GET NEW SLOT ID INTO [X]
STX DCBPSL ; MAKE IT THE "OLD" SLOT
; CURRENT SLOT ID IN [X]
SAMESL: LDA Q7L,X ; GET DRIVE INTO READ MODE
LDA Q6L,X ; READ WITH DELAYS
LDY #8 ; TO SEE IF DRIVE IS SPINNING
RW4: LDA Q6L,X
PHA
PLA
PHA
PLA
STX SLTMP1 ; SAVE SLOT HERE
CMP Q6L,X
BNE RW5
DEY
BNE RW4
RW5: PHP ; SAVE TEST RESULT ON STACK
LDA DRVON,X ; TURN ON MOTOR
LDA #$D8 ; REFRESH
STA DTMP2 ; MOTOR TIME CONSTANT
; CHECK DRIVE ID
LDA DCBDRV
CMP DCBPDR ; HAS DRIVE CHANGED?
BEQ RW7 ; NO, CONTINUE
STA DCBPDR ; ELSE MAKE NEW DRIVE "OLD"
PLP ; SET ZERO FLAG
LDY #0 ; OF TEST RESULT
PHP ; AND PUSH IT BACK ON STACK
RW7: ROR A ; CHECK DRIVE ID
BCC RW8 ; CARRY WILL BE CLEAR IF DRIVE = 2
LDA DRV0EN,X ; ELSE SELECT DRIVE #1
BCS RW9 ; BRANCH ALWAYS
RW8: LDA DRV1EN,X ; SELECT DRIVE #2
RW9: ROR DRVFLG ; HIGH BIT = 1 FOR DRIVE 1, 0 FOR 2
PLP ; CHECK TEST RESULTS
PHP
BNE RW11 ; BRANCH IF DRIVE WAS ON
LDY #7 ; WAIT FOR CAP DISCHARGE
RW10: JSR ARMDEL
DEY
BNE RW10
LDX SLTMP1 ; RESTORE SLOT ID
; SEEK THE TARGET TRACK
RW11: LDA DCBTRK ; GET TARGET TRACK
JSR MYSEEK
PLP ; WAS DRIVE ON?
BNE RW14 ; YES, CONTINUE
; WAIT FOR DRIVE TO COME UP TO SPEED
LDY DTMP2
BPL RW14
RW12: LDY #$12 ; WAIT FOR DRIVE TO
RW13: DEY ; COME UP TO SPEED
BNE RW13
INC DCNT
BNE RW12
INC DTMP2
BNE RW12
; DECODE DISK COMMAND
RW14: LDA DCBCMD ; GET COMMAND
ROR A ; CARRY = 0 IF "READ"
PHP ; SAVE READ/WRITE STATUS
; AND MAINTAIN STACK
BCC GETADR ; BRANCH IF "READ"
JSR PRENIB
; FETCH AN ADDRESS FIELD
GETADR: LDA #48
STA DTMP1 ; INIT RETRY COUNT
GTA0: LDX SLTMP1 ; RESTORE SLOT ID
JSR RDADDR ; GET AN ADDRESS FIELD
BCC RRIGHT ; CONTINUE IF SUCCESSFUL
GTA1: DEC DTMP1 ; ELSE UPDATE RETRY COUNT
BPL GTA0 ; AND TRY AGAIN
; RECALIBRATE THE ARM
GTA2: LDA CTRACK ; SAVE THE
PHA ; CURRENT TRACK ID
LDA #$60
JSR SETTRK
DEC NRECAL ; UPDATE RECAL COUNT
BEQ DRVERR ; ERROR IF EMPTY
LDA #4 ; RESET
STA NSEEK ; SEEK COUNT
LDA #0 ; CALIBRATE THE ARM
JSR MYSEEK ; TO TRACK #0
PLA ; RESTORE CURRENT TRACK
GTA3: JSR MYSEEK ; GO TO IT
JMP GETADR ; AND TRY AGAIN
; ADDRESS FIELD FOUND
RRIGHT: LDY HDRTRK
CPY CTRACK ; ON THE RIGHT TRACK?
BEQ RTTRAK ; YES, CONTINUE
LDA CTRACK
PHA
TYA
JSR SETTRK
PLA
DEC NSEEK
BNE GTA3
BEQ GTA2 ; ELSE RECALIBRATE
; HANDLE A DRIVE ERROR
DRVERR: PLA ; CLEAN UP STACK
LDA #$40 ; $40 = DRIVE ERROR
EREXT: PLP ; CLEAN UP STATUS REGISTER
JMP DERROR
; CHECK FOR PROPER SECTOR (VOLUME CHECK OMITTED)
RTTRAK: LDY DCBSEC
LDA ILEAVE,Y ; GET INTERLEAVE BYTE
CMP HDRSEC ; MATCHED FOUND SECTOR?
BNE GTA1 ; NO, TRY AGAIN
; SECTOR FOUND!
PLP ; WILL THIS BE READ OR WRITE?
BCS DWRITE ; DO "WRITE" IF CARRY SET
; READ A SECTOR
JSR RDSECT ; DO THE READ
BCC GTA3A ; OK
CLC ; RESET FOR NEXT TIME THRU
PHP ; AND PUSH FOR NEXT TIME THRU
BCC GTA1 ; JMP, ERROR OCCURRED
; CHANGED TO ABOVE 4 LINES 6/11/85, CARRY MUST BE CLEARED SO READS
; PHP ; SAVE STATUS
; BCS GTA1 ; ERROR IF CARRY WAS SET
; PLP ; ELSE DUMP STATUS
GTA3A: LDX #$00
STX DTMP3
JSR POSTNB
LDX SLTMP1 ; RESTORE SLOT ID
DONE: LDA #0 ; 0 = NO ERRORS
CLC ; CARRY CLEAR FOR SUCCESS
BCC EXIT
; ERROR EXIT
DERROR: SEC ; CARRY SET FOR ERROR
; GENERAL EXIT
EXIT: STA DCBERR ; SAVE ERROR CODE HERE
LDA DRVOFF,X ; STOP THE DRIVE
RTS ; BYE!
; WRITE A SECTOR
DWRITE: JSR WRTDTA
BCC DONE ; ALL'S WELL IF CARRY CLEAR
LDA #$10 ; ELSE GET ERROR CODE INTO [A]
BNE DERROR ; AND DO AN ERROR EXIT
; ---------------------
; SET UP FOR TRACK SEEK
; ---------------------
MYSEEK: ASL A ; TRACK*2 (PHASE OF DISK CARE)
JSR DOSEEK
LSR CTRACK ; CURRENT TRACK/2
RTS
; --------------
; EXECUTE A SEEK
; --------------
; PAGE BOUNDARY SHOULD BEGIN HERE!
DOSEEK: STA TTRK
JSR XTOY
LDA DR1TBL,Y
BIT DRVFLG
BMI DSE1
LDA DR2TBL,Y
DSE1: STA CTRACK
LDA TTRK
BIT DRVFLG
BMI DSE2
STA DR2TBL,Y
BPL DSE3
DSE2: STA DR1TBL,Y
DSE3: JMP SEEK
; --------------------
; GET SLOT ID INTO [Y]
; --------------------
XTOY: TXA
LSR A
LSR A
LSR A
LSR A
TAY
RTS
; ------------
; SET TRACK ID
; ------------
SETTRK: PHA
LDA DCBDRV
ROR A
ROR DRVFLG
JSR XTOY
PLA
ASL A
BIT DRVFLG
BMI STT1
STA DR2TBL,Y
BPL STT2
STT1: STA DR1TBL,Y
STT2: RTS
; -----------
; IDOS TABLES
; -----------
DR1TBL: DB $00,$00,$00,$00 ; (8 BYTES)
DB $00,$00,$00,$00
CTRACK EQU DR1TBL ; CURRENT TRACK
DR2TBL: DB $00,$00,$00,$00 ; (8 BYTES)
DB $00,$00,$00,$00
NSEEK: DB $00 ; SEEK COUNT
DTMP1: DB $00 ; RETRY COUNT
SLTMP1: DB $00 ; SLOT ID
SLTMP2: DB $00
NRECAL: DB $00 ; RECALIBRATE COUNT
; ----------------------
; MACHINE INITIALIZATION
; ----------------------
INIT: LDA TXTSET ; SET TEXT MODE
LDA MIXCLR ; SET NO MIX
LDA LOWSCR ; SET PAGE 1
LDA #HIGH IOBUFF ; POINT [DCBBFL/H] TO [IOBUFF]
STA DCBBFH
LDA #LOW IOBUFF
STA DCBBFL
LDA #1
STA DCBDRV ; SET DRIVE = 1
STA DCBPDR
RTS
END
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