JNB K1,CASE1
JNB K2,CASE2
JNB K3,CASE3
JNB K4,CASE4
AJMP LOOP
CASE1:
MOV LED,#01111111
CASE2:
MOV LED,#00111111
CASE3:
MOV LED,#00011111
CASE4:
MOV LED,#00001111
K1~K4對應按鍵輸入口,LED對應LED輸出,兩者應為普通IO口