51单片机个IO是否损坏的自检程序，上电后所有IO口每隔一段时间会有一个脉冲输出，用来测试单片机管脚的好坏-51 MCU the IO whether the damage the self-test procedure after power on all IO mouth from time to time there will be a pulse output, used to test the microcontroller pin is good or bad