过8255A读取键盘电平获得输入密码，与预设密码比较，进而实现开锁、报错功能，并控制数显管和指示灯做出相应变化。还可实现密码修改功能-8255A reading level over the keyboard to enter a password to get, compared with the default password, thus achieving unlocking, error function, and control the digital display tubes a