;Commulication Between 89C2051 and PC by RS232
;fosc=12Mhz,BPS=2400
;1Bit START,8Bit DATA,1Bit STOP
;Time count N=230=E6H
DELY1	EQU     0BH
DELY2	EQU     0CH
DELY3	EQU	0DH
DELY4	EQU	0EH


	ORG	0000H
	AJMP	MAIN		;Initial program
	ORG	0023H
	AJMP	SERVE		;Serve port interrupt routine

MAIN:	MOV	TMOD,	#20H	;T1 setup mode 2 (auto reload)
	MOV	TH1,	#0E6H	;time count n=E6H
	MOV	TL1,	#0E6H
	MOV	SCON,	#50H	;serve port setup mode 1 (8bit)
	MOV	PCON,	#80H	;SMOD=1
	SETB	TR1		;start timer T1
	SETB	EA		;enable interrupt
	SETB	ES		;enable serve port interrupt
	MOV	P1,	#7FH
	
	CLR	RI
;Rwait:	JNB	RI,	Rwait
;	MOV	A,	SBUF
;	CLR	RI

;	CPL	P1.6
;	CPL	A
;	MOV	SBUF,	A
;	AJMP	Rwait
	
;	MOV	A,	#78H
;Msend:	jb	p3.5,	Msend
;	clr	ti
;	MOV	SBUF,	A	;send bake data to PC
;	cpl	p1.6
;Mwait:	JNB	TI,	Mwait	;if sender no empty,wait
;	CLR	TI
;	ACALL	D.2S
;	acall	d.2s
;	acall	d.2s
MEND:	AJMP	Mend
	
SERVE:	CLR	EA		;off interrupt
	CLR	RI		;clear recrive interrupt flag
	PUSH	DPH		;bakeup state
	PUSH	DPL
	PUSH	ACC
Recrive:MOV	A,	SBUF	;recrive PC data
	CPL	A
	CPL	P1.6
Send:	MOV	SBUF,	A	;send bake data to PC
Wait:	JNB	TI,	Wait	;if sender no empty,wait
	CLR	TI
Return:	POP	ACC		;restore state
	POP	DPL
	POP	DPH
	SETB	EA		;on interrupt
	RETI			;return
	
D.2S:	MOV 	DELY1,  #20
D.2S_1:	MOV 	DELY2,	#248
D.2S_2:	DJNZ  	DELY2,  D.2S_2
	DJNZ 	DELY1, 	D.2S_1
	RET