8255PC口接8个开关,每0.3秒读一次开关状态,并将其显示在数码管上。(用定时器定时)PC0~PC7 接 K8~K1
P3.1---clk,p3.0---data,clr---+5V
ORG 0000H
AJMP START
ORG 000BH
AJMP IN_T0
ORG 0030H
START: MOV DPTR,#0FF2BH
MOV A,#89H
MOVX @DPTR,A
MOV TMOD,#01H
MOV TH0,#9EH
MOV TL0,#58H
MOV R1,#6
MOV SCON,#0
SETB TR0
SETB ET0
SETB EA
SJMP $
IN_T0: MOV TH0,#9EH
MOV TL0,#58H
DJNZ R1,EXIT
MOV R1,#6
MOV DPTR,#0FF2AH
MOVX A,@DPTR
MOV B,#10H
DIV AB
MOV 10H,B
MOV 11H,A
MOV DPTR,#TAB
MOV A,10H
MOVC A,@A+DPTR
MOV SBUF,A
MOV R2,#5
DJNZ R2,$
MOV A,11H
MOVC A,@A+DPTR
MOV SBUF,A
EXIT: RETI
TAB: DB 0FCH,60H,0DAH,0F2H,66H,0B6H,0BEH,0E0H
DB 0FEH,0F6H,0EEH,3EH,9CH,7AH,9EH,8EH
END