;7447兩位計數器
org 00h
mov r4,#00h
loop: mov p1,r4
call delay
xch a,r4
ADD A,#01
DA A
XCH A,R4
JMP LOOP
DELAY: MOV R5,#50
D1: MOV R6,#40
D2:MOV R7,#248
DJNZ R7,$
DJNZ R6,D2
DJNZ R5,D1
RET
END