A microprocessor-controlled door lock system

The detailed design of a microprocessor-based door lock system including the hardware design, software functional definitions, and diagnostics is presented. The system is designed in two modules: a door lock controller board, in which all functions necessary for keyless entry at a door are implemented, and a programming board. There is only one such board for the whole dwelling and it has additional hardware such as serial link interface circuitry and a display. The two modules are connected temporarily to perform keycode modification and diagnostic functions using a serial data link. The keycode is a four-character pattern. Authorized users of the dwelling are given this code and are required to enter this pattern via a keypad for entry. The number of integrated circuits used was kept to a minimum (seven are used for the door board). The system uses 2240 B of EPROM, 4 B of EEPROM, and 90 B of RAM. The lock solenoid driver circuitry was significantly reduced by using a solid-state relay, and the system uses 2.4576-MHz crystal. An internal divide-by-four circuit provides a bus speed of 614.4 kHz. This relatively low frequency reduces the system cost by allowing the slowest access memory parts to be used. This speed is adequate for the door lock system operation.<
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