PAGE
	SBTTL "--- MACHINE-DEPENDENT I/O: ATARI ---"

	; ----------------------------
	; FETCH ASCII KEYCODE INTO [A]
	; ----------------------------

	; EXIT: ASCII IN [A] & [IOCHAR]

BADKEY:	JSR	BOOP
	JMP	GKEY0

GETKEY:	CLD
	TXA			; SAVE [X] & [Y]
	PHA
	TYA
	PHA

GKEY0:	LDA	#0
	STA	BLINK+LO	; LENGTHEN BLINK DELAY
	STA	BLINK+HI	; TO MAXIMUM

	LDA	COLCRS+LO	; CALC CURSOR X-POS
	ASL	A
	ASL	A
	CLC
	ADC	#48
	STA	HPOSM0

	LDA	ROWCRS		; CALC CURSOR Y-POS
	ASL	A
	ASL	A
	ASL	A
	CLC
	ADC	#39
	TAY			; MOVE HERE FOR DRAWING

	LDA	#%00000011	; FORCE CURSOR "ON"
	STA	CSHAPE
	STA	MISSL,Y		; AND DRAW IT

GKEY1:	LDX	CH		; CHECK HARDWARE FOR A KEYPRESS

	INC	BLINK+LO
	BNE	NOBLIN
	INC	BLINK+HI
	BNE	NOBLIN

	LDA	#$80
	STA	BLINK+HI	; RESET BLINK TIMER

	LDA	CSHAPE
	EOR	#%00000011
	STA	CSHAPE		; FLIP CURSOR SHAPE
	STA	MISSL,Y		; DRAW CURSOR INTO MISSILE RAM

NOBLIN:	CPX	#$FF		; KEY PRESSED?
	BEQ	GKEY1		; NO, KEEP SCANNING

	LDA	#$FF
	STA	CH		; RESET KEY HARDWARE

	TXA
	BMI	BADKEY		; REJECT CTRL KEYS

	LDA	ATASCI,X	; GET CODE INTO [A]
	CMP	#EOL		; WAS IT EOL?
	BEQ	CLICK		; OKAY IF SO
	TAX			; ANY OTHER NEGATIVE CODE
	BMI	BADKEY		; IS ILLEGAL

	; ERASE CURSOR, "CLICK" THE SPEAKER

CLICK:	STA	IOCHAR		; SAVE KEYCODE
	LDA	#0
	STA	MISSL,Y		; ERASE CURSOR

	LDY	#$80
CLK0:	STY	CONSOL
	LDX	#8
CLK1:	DEX
	BNE	CLK1
	DEY
	BNE	CLK0

	PLA			; RESTORE
	TAY			; EVERYTHING
	PLA
	TAX
	LDA	IOCHAR		; GET CHAR INTO [A]
	RTS			; AND RETURN IT

	; -----------------
	; PRINT CHAR IN [A]
	; -----------------

CHAR:	STA	IOCHAR		; SAVE HERE
	TXA			; SAVE [X] AND [Y]
	PHA
	TYA
	PHA

	LDY	ROWCRS		; Y-POS INTO [Y]
	LDX	COLCRS+LO	; X-POS INTO [X]

	LDA	IOCHAR		; RESTORE CHAR
	CMP	#EOL		; IS IT EOL?
	BEQ	OUTEOL		; YES, SPECIAL HANDLING
	CMP	#$0D		; ALSO CHECK FOR
	BEQ	OUTEOL		; ASCII EOL

	; HANDLE A NON-EOL CHAR

	CPY	#YSIZE-1	; ON LAST SCREEN LINE?
	BCC	NOSCRL		; NO, NO SCROLL NEEDED
	CPX	#XSIZE		; LAST CHAR ON LINE?
	BCC	NOSCRL		; NO, DON'T SCROLL

	; SCROLL THE SCREEN

DOSCRL:	DEY			; PUSH CURSOR UP ONE LINE
	STY	ROWCRS

	LDX	SLINE		; GET CURRENT SCROLL LINE

SRL0:	CPX	#YSIZE
	BEQ	SRL2		; SCROLL DONE

	LDA	LOLINE,X	; GET ADDR OF DEST LINE
	STA	LTO+LO		; INTO [LTO]
	LDA	HILINE,X
	STA	LTO+HI

	INX
	LDA	LOLINE,X	; GET ADDR OF SOURCE LINE
	STA	LFROM+LO	; INTO [LFROM]
	LDA	HILINE,X
	STA	LFROM+HI

	LDY	#XSIZE
SRL1:	LDA	(LFROM),Y	; MOVE SOURCE LINE
	STA	(LTO),Y		; TO DEST LINE
	DEY
	BPL	SRL1

	BMI	SRL0		; LOOP TILL [X] = YSIZE

SRL2:	LDX	#XSIZE
	LDA	#0
SRL3:	STA	SCREEN+920,X	; CLEAR LAST LINE
	DEX			; OF SCREEN RAM
	BPL	SRL3

NOSCRL:	LDA	IOCHAR		; RESTORE CHAR
	LDX	#$0B		; CIO "PUT CHAR"
	STX	ICCOM		; COMMAND
	LDX	#0		; IOCB #0 (E:)
	STX	ICBLEN+LO	; ZERO THE
	STX	ICBLEN+HI	; BUFFER LENGTH
	JSR	CIOV		; SEND IT OUT!

	PLA			; RESTORE [X] AND [Y]
	TAY
	PLA
	TAX
	RTS

	; HANDLE EOL

OUTEOL:	LDA	#$9B		; MAKE SURE [IOCHAR]
	STA	IOCHAR		; IS AN ATASCII EOL
	CPY	#YSIZE-1	; LAST SCREEN LINE?
	BCC	NOSCRL		; NO, DON'T SCROLL
	BCS	DOSCRL		; ELSE SCROLL

	; ---------------------
	; FETCH A LINE OF INPUT
	; ---------------------

	; ENTRY: ABS ADDR OF READ BUFFER IN [ARG1]
	; EXIT: # CHARS READ IN [A]

INPUT:	JSR	LINOUT		; FLUSH [LBUFF]

	LDY	#$FF
	STY	CH		; CLEAR KEYBOARD
	INY			; = 0
	STY	LINCNT		; RESET LINE COUNT

INLOOP:	JSR	GETKEY		; GET ASCII INTO [A] AND [IOCHAR]

	CMP	#EOL		; EOL?
	BEQ	ENDLIN		; LINE DONE IF SO
	CMP	#BACKSP		; BACKSPACE?
	BEQ	BACKUP		; SPECIAL HANDLING

	STA	LBUFF,Y		; ELSE ADD CHAR TO INPUT BUFFER
	INY			; NEXT POSITION IN LINE

SHOWIT:	JSR	CHAR		; SEND TO SCREEN

	CPY	#77		; 2 SCREEN LINES FULL?
	BCC	INLOOP		; NO, GET ANOTHER CHAR

	; HANDLE LINE OVERFLOW

NOMORE:	JSR	GETKEY
	CMP	#EOL		; IF EOL,
	BEQ	ENDLIN		; WRAP UP THE LINE
	CMP	#BACKSP		; BACKSPACE
	BEQ	BACKUP		; IS OKAY TOO
	JSR	BOOP		; ELSE COMPLAIN
	JMP	NOMORE		; AND INSIST

	; HANDLE BACKSPACE

BACKUP:	DEY			; BACK UP THE POINTER
	BPL	SHOWIT		; SEND BS IF NOT START OF LINE
	JSR	BOOP		; ELSE SCREAM WITH PAIN
	LDY	#0		; RESET POINTER
	BEQ	INLOOP		; AND WAIT FOR SOMETHING BETTER

	; HANDLE END OF LINE

ENDLIN:	STA	LBUFF,Y		; SHIP EOL TO BUFFER
	INY			; UPDATE INDEX
	STY	LINLEN		; SAVE HERE FOR "READ"
	STY	PRLEN		; AND HERE FOR "PPRINT"

	JSR	CHAR		; AND SEND EOL TO SCREEN

	; MOVE [LBUFF] TO [ARG1] W/LC CONVERSION

LEX0:	LDA	LBUFF-1,Y	; GET A CHAR FROM [LBUFF]

	CMP	#EOL		; ATASCII EOL?
	BNE	LEX1		; IF SO,
	LDA	#$0D		; CONVERT TO ASCII
	BNE	LEX2

LEX1:	CMP	#'A'		; IF CHAR IS ALPHA,
	BCC	LEX2		; CONVERT TO LOWER CASE
	CMP	#'Z'+1
	BCS	LEX2
	ADC	#$20

LEX2:	STA	(ARG1),Y	; MOVE CHAR TO INPUT BUFFER AT [ARG1]
	DEY			; LOOP TILL
	BPL	LEX0		; ALL CHARS MOVED

	JSR	PPRINT		; SCRIPT [LBUFF] IF ENABLED

	LDA	LINLEN		; RESTORE # CHARS
	RTS			; INTO [A]

	; -----------------------
	; DIRECT PRINT LINE [X/A]
	; -----------------------

	; ENTRY: STRING ADDRESS IN [X/A] (LSB/MSB)
	;        STRING LENGTH IN [Y]

DLINE:	STX	STRING+LO	; DROP STRING ADDRESS
	STA	STRING+HI	; INTO DUMMY BYTES

	LDX	#0		; INIT CHAR-FETCH INDEX

DOUT:	DB	$BD		; 6502 "LDA nnnn,X" OPCODE
STRING:	DW	$0000		; DUMMY OPERAND BYTES
	JSR	CHAR
	INX
	DEY			; LOOP TILL
	BNE	DOUT		; OUT OF CHARS

	RTS

	; -----------------------
	; SEND [LBUFF] TO PRINTER
	; -----------------------

	; ENTRY: LENTH OF LINE IN [PRLEN]

PNAME:	DB	"P:"		; FILENAME FOR PRINTER
	DB	EOL

SFLAG:	DB	0		; PREVIOUS SCRIPTING STATE

PPRINT:	LDA	SCRIPT		; SCRIPTING INTERNALLY ENABLED?
	BEQ	PEX		; NO, SCRAM IMMEDIATELY

	LDA	ZBEGIN+ZSCRIP+1	; CHECK SCRIPT FLAG
	AND	#%00000001	; SCRIPTING ON?
	BEQ	PEX		; NO, EXIT

	LDA	PSTAT		; CHECK PRINTER STATUS
	BMI	PEX		; CAN'T OPEN IF NEGATIVE
	BNE	PP1		; ALREADY OPEN, SCRIPT THE LINE

	; OPEN THE PRINTER FOR OUTPUT

	JSR	CLOSEP		; CLOSE IOCB #1 FIRST FOR SAFETY

	LDX	#$10		; IOCB #1 (P:)
	LDA	#LOW PNAME	; POINT
	STA	ICBADR+LO,X	; TO
	LDA	#HIGH PNAME	; P:
	STA	ICBADR+HI,X	; FILENAME
	LDA	#$03		; CIO "OPEN"
	STA	ICCOM,X		; COMMAND
	LDA	#$08		; SET CHANNEL
	STA	ICAUX1,X	; FOR WRITE-ONLY
	LDA	#0
	STA	ICAUX2,X	; ZERO THIS BYTE
	JSR	CIOV		; OPEN IT!
	TYA			; STATUS CODE IN [Y]
	BMI	BADP		; ERROR IF NEGATIVE

	LDA	#$70
	STA	POKMSK
	STA	IRQEN		; DISABLE BREAK KEY

	LDA	#1		; SET [PSTAT]
	STA	PSTAT		; TO INDICATE "PRINTER READY"

	; PRINT [LBUFF]

PP1:	LDX	#$10		; IOCB #1 (P:)
	LDA	#LOW LBUFF	; TELL CIO
	STA	ICBADR+LO,X	; WHERE
	LDA	#HIGH LBUFF	; [LBUFF]
	STA	ICBADR+HI,X	; IS HIDING
	LDA	PRLEN		; # CHARS TO PRINT
	STA	ICBLEN+LO,X
	LDA	#0		; CLEAR THE
	STA	ICBLEN+HI,X	; MSB OF LINE LENGTH
	LDA	#$0B		; CIO "PUT BUFFER" COMMAND (BM 4/9/85)
	STA	ICCOM,X		; COMMAND
	JSR	CIOV
	TYA
	BPL	PEX		; EXIT IF NO ERROR

	; HANDLE PRINTER ERROR

BADP:	LDA	#$FF		; SET PRINTER STATUS
	STA	PSTAT		; TO "CAN'T OPEN"

	; CLOSE PRINTER CHANNEL (IOCB #1)

CLOSEP:	LDX	#$10		; IOCB #1 (P:)
	LDA	#$0C		; CIO "CLOSE"
	STA	ICCOM,X		; COMMAND
	JSR	CIOV		; CLOSE THE CHANNEL

PEX:	RTS

	; ------------
	; SPLIT SCREEN
	; ------------

	; SPLIT SCREEN AT LINE [ARG1]
	; DISABLE SPLIT IF [ARG1] = 0
	; IGNORE IF SPLIT ALREADY ENABLED OR [ARG1] >= 20

ZSPLIT:	LDX	ARG1+LO		; IF [ARG1] = 0,
	BEQ	OFFSPL		; TURN OFF SPLIT SCREEN

	LDA	SPSTAT		; SPLIT ALREADY ENABLED?
	BNE	SPLEX		; IGNORE REQUEST IF SO

	CPX	#20		; IF [ARG1] >= 20,
	BCS	SPLEX		; IGNORE

	INX
	STX	SLINE		; ELSE SET NEW SPLIT LINE
	STX	SPSTAT		; SET "SPLIT ENABLED" FLAG

SPL0:	LDA	LOLINE,X	; MAKE [LFROM] POINT TO
	STA	LFROM+LO	; LINE [X] IN WINDOW
	LDA	HILINE,X
	STA	LFROM+HI

	LDY	#XSIZE		; CLEAR LINE [X]
	LDA	#0
SPL1:	STA	(LFROM),Y
	DEY
	BPL	SPL1

	DEX			; DONE ALL LINES?
	BNE	SPL0		; LOOP TILL WINDOW CLEARED
	STX	LINCNT		; RESET LINE COUNT TO ZERO

SPCALC:	LDA	#YSIZE-1	; CALCULATE # LINES TO SCROLL
	SEC			; BEFORE "MORE" APPEARS:
	SBC	SLINE		; LMAX = YSIZE-SLINE-1
	STA	LMAX
	DEC	LMAX

SPLEX:	RTS

	; --------------------
	; DISABLE SPLIT SCREEN
	; --------------------

OFFSPL:	JSR	TOBOT1		; SET CURSOR TO BOTTOM

SPLOFF:	LDX	#1
	STX	SLINE		; SPLIT AT LINE 1
	DEX			; = 0
	STX	SPSTAT		; TURN OFF STATUS FLAG
	STX	LINCNT		; RESET LINE COUNT
	LDA	#21
	STA	LMAX		; SET MAXIMUM LINE SCROLL
	BNE	NEWLOG		; RESET LINE MAP & RETURN

	; ------
	; SCREEN
	; ------

	; GO TO TOP WINDOW IF [A] = 0
	; GO TO BOTTOM IF [A] = 1
	; IGNORE IF SPLIT NOT ENABLED OR [A] <> 0 OR 1

ZSCRN:	LDA	SPSTAT		; IF SPLIT NOT ENABLED,
	BEQ	SPLEX		; IGNORE REQUEST

	LDA	ARG1+LO		; IF [ARG1] = 0,
	ORA	ARG1+HI
	BEQ	TOBOT0		; GO TO BOTTOM WINDOW
	CMP	#1		; IF [ARG1] <> 1,
	BNE	SPLEX		; IGNORE THE REQUEST

	; SET TO TOP WINDOW

TOTOP:	LDY	#21		; TEMPORARILY RESET
	STY	LMAX		; [LMAX] TO KILL "MORE"
	LDY	#1		; Y-POS = 1
	BNE	DOSCRN

	; SET TO BOTTOM WINDOW

TOBOT0:	JSR	SPCALC		; RE-CALC [LMAX]

TOBOT1:	LDY	#23		; Y-POS = 23

DOSCRN:	STY	ROWCRS		; Y-POS = [Y]
	LDA	#0		; X-POS = 0
	STA	COLCRS+LO
	STA	LINCNT		; RESET LINE COUNT

	; FALL THROUGH ...

	; ----------------------
	; RESET LOGICAL LINE MAP
	; ----------------------

NEWLOG:	LDA	#$FF
	STA	LOGMAP
	STA	LOGMAP+1
	STA	LOGMAP+2
	RTS

	; ---------
	; RAZZ USER
	; ---------

BOOP:	LDA	#200		; SET
	STA	AUDF1		; FREQUENCY
	LDA	#$AA		; PURE TONE, VOLUME #10
	STA	AUDC1
	LDA	#252		; 4 JIFFY DELAY
	STA	RTCLOK
BOOP0:	LDA	RTCLOK
	BNE	BOOP0
	STA	AUDC1		; SHUT OFF SOUND
	RTS

	; ------------
	; CLEAR SCREEN
	; ------------

CLS:	LDA	#LOW SCREEN
	STA	I+LO
	LDA	#HIGH SCREEN	; POINT [I] TO
	STA	I+HI		; SCREEN RAM

	LDA	#0
	STA	LENGTH		; RESET LINE LENGTH
	TAY
	LDX	#4		; CLEAR 4 PAGES
CLS0:	STA	(I),Y		; FOR SCREEN
	INY
	BNE	CLS0
	INC	I+HI		; POINT TO NEXT PAGE
	DEX			; 4 PAGES DONE?
	BNE	CLS0		; LOOP TILL EMPTY

	LDY	#1		; SET Y-POS TO 1
	STY	ROWCRS
	DEY			; X-POS TO 0
	STY	COLCRS+LO
	JMP	SPLOFF		; DISABLE SPLIT-SCREEN & RETURN

	; -------------------
	; LINE ADDRESS TABLES
	; -------------------

LOLINE:	DB	$40,$68,$90,$B8,$E0,$08,$30,$58
	DB	$80,$A8,$D0,$F8,$20,$48,$70,$98
	DB	$C0,$E8,$10,$38,$60,$88,$B0,$D8

HILINE:	DB	$BC,$BC,$BC,$BC,$BC,$BD,$BD,$BD
	DB	$BD,$BD,$BD,$BD,$BE,$BE,$BE,$BE
	DB	$BE,$BE,$BF,$BF,$BF,$BF,$BF,$BF

	; ------------------------
	; ATASCII CONVERSION TABLE
	; ------------------------

ATASCI:	DB	$6C,$6A,$3B,$FF,$FF,$6B,$FF,$FF		; UNSHIFTED
	DB	$6F,$FF,$70,$75,$9B,$69,$2D,$FF
	DB	$76,$FF,$63,$FF,$FF,$62,$78,$7A
	DB	$34,$FF,$33,$36,$FF,$35,$32,$31
	DB	$2C,$20,$2E,$6E,$FF,$6D,$2F,$FF
	DB	$72,$FF,$65,$79,$FF,$74,$77,$71
	DB	$39,$FF,$30,$37,$7E,$38,$FF,$FF
	DB	$66,$68,$64,$FF,$FF,$67,$73,$61

	DB	$4C,$4A,$3A,$FF,$FF,$4B,$FF,$FF		; SHIFTED
	DB	$4F,$FF,$50,$55,$9B,$49,$2D,$FF
	DB	$56,$FF,$43,$FF,$FF,$42,$58,$5A
	DB	$24,$FF,$23,$36,$FF,$35,$22,$21
	DB	$2C,$20,$2E,$4E,$FF,$4D,$3F,$FF
	DB	$52,$FF,$45,$59,$FF,$54,$57,$51
	DB	$39,$FF,$30,$27,$7E,$38,$FF,$FF
	DB	$46,$48,$44,$FF,$FF,$47,$53,$41

	END