基于c51的汇编超声波测距仪程序

ORG 0000H
    AJMP  MAIN
	ORG   000BH
	AJMP  T8ms
	ORG   0100H
MAIN:  MOV  TMOD,#10H
       MOV  TL0,#00H
	   MOV  TH0,#00H
	   MOV  R7,#00H
	   MOV  P2,#00H
	   CLR  P1.1
	   MOV  R6,#250
	   SETB  EA
	   SETB  ET0
	   SETB  TR0
	   AJMP  $

	   
	   ORG  00150H
T8ms:  CLR  TR0
       CJNE R7,#00H,BIT1
	   CLR  P2.3
	   MOV  P0,70H
	   SETB P2.0
	   MOV  R7,#01H
	   JMP  BACK0
BIT1:  CJNE R7,#01H,BIT2
       CLR  P2.0
	   MOV  P0,71H
	   SETB P2.1
	   MOV  R7,#02H
	   JMP  BACK0
BIT2:  CJNE R7,#02H,BIT3
       CLR  P2.1
	   MOV  P0,72H
	   SETB P2.2
	   MOV  R7,#03H
	   JMP  BACK0
BIT3:  CLR  P2.2
	   MOV  P0,73H
	   SETB P2.3
	   MOV  R7,#00H
BACK0: DJNZ R6,BACK1
       ACALL SERVEY
	   NOP
BACK1: MOV  TL0,#00H
       MOV  TH0,#00H
	   SETB TR0
	   RETI


	   ORG  0300H
SERVEY:SETB P1.1
       ACALL DELAY25ms
	   MOV  TH1,#00H
	   MOV  TL1,#00H
	   CLR  P1.1
	   SETB TR1
LOOP:  JB P3.3,LOOP
       CLR  TR1
	   MOV  61H,TH1
	   MOV  60H,TL1
	   MOV  A,60H
	   MOV  B,#17
	   MUL  AB
	   MOV  60H,A
	   MOV  A,61H
	   MOV  61H,B
	   MOV  B,#17
	   MUL  AB
	   ADD  A,61H
	   MOV  61H,A
	   MOV  A,B
	   ADDC A,#00H
	   MOV  62H,A
	   MOV  R5,#24
	   MOV  50H,#00H
	   MOV  51H,#00H
	   MOV  52H,#00H
BCDLOOP: CLR  C
         MOV  A,60H
		 RLC  A
		 MOV  60H,A
		 MOV  A,61H
		 RLC  A
		 MOV  61H,A
		 MOV  A,62H
		 RLC  A
		 MOV  62H,A
		 MOV  A,50H
		 ADDC A,50H
		 DA   A
		 MOV  50H,A
		 MOV  A,51H
		 ADDC A,51H
		 DA   A
		 MOV  51H,A
		 MOV  A,52H
		 ADDC A,52H
		 DA   A
		 MOV  52H,A
		 DJNZ R5,BCDLOOP
		 SWAP A
		 ANL  A,#0FH
		 MOV  DPTR,#TAB
		 MOVC A,@A+DPTR
		 MOV  73H,A
		 MOV  A,52H
		 ANL  A,#0FH
		 MOVC A,@A+DPTR
		 MOV  72H,A
		 MOV  A,51H
		 SWAP A
		 ANL  A,#0FH
		 MOVC A,@A+DPTR
		 MOV  71H,A
		 MOV  A,51H
		 ANL  A,#0FH
		 MOVC A,@A +DPTR
		 MOV  70H,A
		 RET


		 ORG  0450H
		 DELAY25ms:
		 MOV  R4,50H
LOOP3:   MOV  R3,#0FH
LOOP4:   NOP
         NOP
		 NOP
		 NOP
		 DJNZ R3,LOOP4
		 DJNZ R4,LOOP3
		 RET

TAB:DB  3FH,06H,5BH,4FH,66H,6DH,7DH,07H
	DB  7FH,6FH,77H,7CH,39H,5EH,79H,71H
	END