Microcomputer application system, usually using mechanical contact key switch, its main function is to convert the mechanical off electrical logic. That is, it provides a standard TTL logic level, in order to be compatible with the logic level of the general purpose digital system. In addition, in addition to the reset button the dedicated reset circuit and loyal reset function, other keys to set the switch state control function or input data. When the set function keys or numeric keys is pressed, the computer application system should be set to complete the key. Therefore, the key information input process is closely related to the software architecture. For a set of keys or a keyboard, connected with the microcontroller through the interface circuit. SCM can be used to query or to understand whether the key input interrupt and check which key was pressed, if any key is pressed, jump to the corresponding keyboard handler to perform at, if no key is pressed to continue to execute other programs.