ch12_s2.asm

51单片机基础篇 对于有一定基础的人看看 包含书中所以的源代码

     ;PROGRAM NAME S2.ASM
     ;TEST SERIAL OUTPUT PORT SIMULATION
     ;
     BUZZER 	REG     	P3.4
     LED    	REG     	P3.7
     ;
     RESET  	MOV     	R0,#00H
             	DJNZ    	R0,$
             	CLR     	BUZZER
             	CLR     	BUZZER
     ;
             	SETB    	P3.0            ;RXD=1
             	SETB    	P3.1            ;TXD=1
     AGAIN   	MOV     	R7,#81H
             	MOV     	R6,#AAH
             	LCALL   	SERIAL_OUT
             	LCALL   	DELAY
             	SJMP    	AGAIN
     ;
     SERIAL_	OUT
             	CLR     	C
             	MOV     	A,R7
             	LCALL   	SENDBYT
             	NOP
             	NOP
             	NOP
             	CLR     	C
             	MOV     	A,R6
             	LCALL   	SENDBYT
             	RET
     ;
     SENDBYT 	MOV     	R0,#08H
     SBIT    	RRC     	A
             	JC      	OUT1
     OUT0    	LCALL   	OUTLO
             	SJMP    	SENDNXT
     OUT1    	LCALL   	OUTHI
     SENDNXT 	DJNZ    	R0,SBIT
             	RET
     ;
     OUTLO  	CLR     	P3.0
             	LCALL   	PULSE
             	RET
     ;
     OUTHI   	SETB    	P3.0
             	LCALL   	PULSE
             	RET
     ;
     PULSE   	SETB    	P3.1
             	CLR     	P3.1
             	NOP
             	NOP
             	SETB    	P3.1
             	RET
     ;
     DELAY   	MOV     	R0,#0
     $1      	MOV     	R1,#0
             	DJNZ    	R1,$
             	DJNZ    	R0,$1
             	RET