8253_2.asm

基于89s51的一通用平台

2, 测量信号频率
START:	CLR  P1.0
			MOV DPTR,#8353H
			MOV A,#0B4H
			MOVX @DPTR,A
			MOV DPTR,#8253-2
			MOV A,#0B8H
			MOVX @DPTR,A
			MOV A,#00H
			MOVX @DPTR,A
			MOV DPTR,#8253-2
			MOV A,#72H
			MOVX @DPTR,A
			MOV A,#20H
			MOVX @DPTR,A
MOV DPTR,#8253-2
			MOV A,#4EH
			MOVX @DPTR,A
			MOV A,#30H
			MOVX @DPTR,A
			SETB P1.0
			CLR  P1.0
			ACALL D10MS
			MOVX A,@DPTR
			CPL A
			ADD A,#01H
			MOV B,A
			MOVX A,,@DPTR
			CPL A
			JC	PLUS
			SJMP $
PLUS:	INC A
			SJMP $
DA0MS:	MOV R6,#64H
D10MS1:	MOV R7,#19H
			DJNZ R7,$
			DJNZ R6,D10MS1
			RET