A unique interface adapter is coupled to a microprocessor by a three-wire self-clocking serial data bus for accommodating a twenty-key keyboard and an eight-digit display. The interface adapter includes circuitry for recovering a clock signal and a non-return-to-zero (NRZ) data signal from the data signal...http://www.google.com.hk/patents/US4398265?utm_source=gb-gplus-share專利 US4398265 - Keyboard and display interface adapter architecture
