HD68P05V07 Software Serial 'HELLO, WORLD'.

HELLO05.asm

*	HELLO05
*
*	SYSTEM DEFINITIONS
PORTA	EQU	$00
PORTB	EQU	$01
PORTC	EQU	$02
*
PUT	EQU	PORTC
IN	EQU	2
OUT	EQU	3
*
*	VERIABLES
	ORG	$0020
RSAVE	RMB	1
COUNT	RMB	1
*
*	MESSAGE
	ORG	$0080
HELLO	FCB	'HELLO, WORLD',$0D,$0A,$00
*
*	INITIALIZE
RESET	BSET	OUT,PUT		INITIAL VALUE
	BSET	OUT,PUT+4	DIRECTION
	BCLR	IN,PUT+4	DIRECTION
*
*	HELLO, WORLD
	LDX	#0
PUTS	LDA	HELLO,X
	BEQ	LOOP
	JSR	PUTC
	INCX
	BRA	PUTS
*
*	ECHO BACK TEST
LOOP	JSR	GETC
	JSR	PUTC
	BRA	LOOP
*
*	DELAY
DELAY	DECX		4
	BNE	DELAY	4
	RTS		6+7(JSR)
*
*	INPUT ROUTINE, 104 CYCLES PER BIT.
GETC	BRCLR	IN,PUT,*	MAKE SURE IT'S HIGH
	BRSET	IN,PUT,*	10	WAIT FOR START
	STX	RSAVE		5 (15)	SAVE X VALUE
	LDX	#8		2 (17)	8 BITS TO READ
	STX	COUNT		5 (23)
	LDX	#4		2 (25)
	BSR	DELAY		45 (70)
	TST	X		6 (76)	0.5 BIT TIME +24
*
INBT	LDX	#7		2 (26)
	BSR	DELAY		69 (95)
	TST	1,X		7 (102)
	NOP			2 (104)
	BRCLR	IN,PUT,*+3	10	READ
	RORA			4 (14)	SAVE BIT
	DEC	COUNT		6 (20)
	BNE	INBT		4 (24)
*
	LDX	#13		2
	JSR	DELAY		117 (119)
	LDX	RSAVE		6 (125)	RESTORE X VALUE
	RTS			6 (131)
*
*	OUTPUT ROUTINE, 104 CYCLES PER BIT.
PUTC	BSET	OUT,PUT	MAKE SURE IT'S HIGH
	STX	RSAVE	SAVE X VALUE
	LDX	#10	10 BITS TO SEND
	STX	COUNT	START,8 DATA,STOP
	CLC		START A ZERO
	BRA	STAR
*
OUTBT	LDX	#7	2 (27)
	JSR	DELAY	69 (96)
	NOP		2 (98)
	SEC		2 (100)	FILL WITH ONES FOR STOP
	RORA		4 (104)	GET A BIT
*
STAR	BCS	OU1	4 (4)	1?
	BCLR	OUT,PUT	7 (11)	NO
	BRA	OBD	4 (15)
OU1	BSET	OUT,PUT	7 (11)	YES
	BRA	OBD	4 (15)
OBD	DEC	COUNT	6 (21)
	BNE	OUTBT	4 (25)	DONE?
	LDX	RSAVE	RESTORE X VALUE
	RTS
*
*	VECTORS
DUMMY	RTI
	ORG	$0FF8
	FDB	DUMMY
	FDB	DUMMY
	FDB	DUMMY
	FDB	RESET
*
	END