超声波测距ASM 测试 好用！

;晶振采用6M,P1口为数码管段输出口,P3.0~P3.2为数码管位输出口,P3.5超声波发送输出,P3.7超声波接收。
;超声波测距

;;;;;;;;;;;;;;中断入口程序;;;;;;;;;;;;;;;;;;;;;;;;;;

 ORG 0000H
 LJMP START
 ORG 002BH
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;主程序;;;;;;;;;;;;;;;;;

START: MOV R0,#70H
 MOV R7,#0BH
 MOV 20H,#00H
CLEARDISP: MOV @R0,#00H
 INC R0
 DJNZ R7,CLEARDISP
 MOV TMOD,#99H
CJZCX: MOV TL0,#00H
 MOV TH0,#00H
 MOV R0,#0BH
 MOV R1,#0BH
 MOV 16H,#03H
 MOV 15H,#54H
 MOV 17H,#90H
PUZEL: MOV 14H,#32H ;超声波发射持续200MS
HERE: CPL P3.5 ;输出40KHZ方波
 NOP
 NOP
 NOP
 DJNZ 14H,HERE

 SETB TR0
 SETB P3.2
MQ: DJNZ 15H,$
 DJNZ 16H,MQ
QBA: JNB P3.7,QBC
 DJNZ R1,QBA
 DJNZ R0,QBA
QBC: DJNZ 17H,QBC
 CLR P3.2
 CLR TR0
 MOV 70H,TL0
 MOV 71H,TH0
 MOV R2,71H
 MOV R3,70H
 MOV R6,#22H
 MOV R7,#0H
 LCALL MULD
 MOV R6,#64H
 MOV R7,#0H
 LCALL DIVD
 MOV 73H,R2
 MOV 74H,R3

 MOV R6,73H
 MOV R7,74H
 LCALL HB2
 MOV A,R4
 MOV B,#10H
 DIV AB
 MOV 78H,A