89C52 汇编 计数器实验

	ORG 0000H
	SJMP START
	ORG 000BH
	SJMP LOOP;中断入口
	RETI
START:	
	MOV P2,#11111111B
	MOV SP,#0FFH
	MOV DPTR,#SEG_TAB
	SETB EA
	MOV TMOD,#06H 
	MOV TCON,#010H
	SETB ET0
	SETB TR0
	SETB RS0
	SETB RS1
	MOV P0,#03FH
	MOV R3,#0
	MOV R1,#0
	MOV R4,#00FH
	MOV TH0,#0FBH
	MOV TL0,#0FBH
	MOV A,#0
	AJMP ST
ST:	
	JB P3.2,$
	INC R1
	MOV A,R1
	CPL A
	RL A
	RL A
	RL A
	RL A
	RL A;让高三位显示，左移五次
	MOV P2,A
	JNB P3.2,$
	AJMP ST
LOOP:	
	PUSH ACC
	PUSH PSW;保护数据
	SETB RS1
	SETB RS0
	MOV R1,#0
	INC  R3
	MOV  A,R3
	MOVC A,@A+DPTR
	MOV P0,A
	POP PSW
	POP ACC
	RETI

SEG_TAB:DB 03FH,006H,05BH,04FH;字形表0~3
	DB 066H,06DH,07DH,007H;字形表4~7
	DB 07FH,06FH,077H,07CH
	DB 039H,05EH,079H,071H
	END