一、开机显示代码“301”分析与检修:按动ESC键,检查信号线JRQ_1、CLOCK、QA～QH信号均正常。检测8255芯片B口的PB_7与PB_6正常状态是01,但按键一次有变化。可判断8255芯片性能变坏,速度达不到要求。换下该8255芯片试之,则将故障消除。二、有一IBM键盘系统联机后敲键输入数据信息,发现有一部分按键输入失灵 First, the boot code “301” Analysis and Maintenance: Press the ESC key, check the signal line JRQ_1, CLOCK, QA ~ QH signals are normal. 8255 chip B port detection PB_7 and PB_6 normal state is 01, but the key changes. Can determine the 8255 chip performance deterioration, speed can not meet the requirements. Replace the 8255 chip test, the fault will be eliminated. Second, there is an IBM keyboard system after typing the keyboard input data and found some of the key input failure