从8255的C口低四位输入一个BCD码，高四位也输入一个BCD码，两者相加后，以BCD码的形式从A口输出到指示灯。CS接280H。-From the 8255 low of C 4 I enter a BCD code, the high-four also enter a BCD code, the two add up to the form of BCD code output from the A to the light. CS then 280H.