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To improve fuel efficiency in a conventional gasoline engine, Toyota Motor Corporation has developed and mass-produced a continuously-variable valve lift (CVVL) system that reduces the pumping loss at low engine load by continuously changing the stroke of the intake valve of the engine. The electronic driver unit (EDU) controls the actuator in an integrated structure. In the EDU, the application specific integrated circuit (ASIC) has an important function to control the motor and to secure failsafe by executing mutual watch with the CPU. We developed this ASIC by using silicon on insulator (SOI) processes suitable for the high temperature system requirements.

In the field of automotive body electronic control such as control of door locks, power windows, and wipers, there is a growing need of multiplexing communication to reduce the amount of wire harnesses. To meet this need, we developed a multiplexing communication protocol particularly suited to the body electronic control. Based on the developed protocol, we designed a communication control IC and a simple driver/receiver circuit with a few discrete components. The bus access method of the communication is the CSMA/CD with nondestructive bit arbitration, and its bit rate is 5 kbps. Its transmission media is a single wire. The communication IC has a multiplexing control block and a serial I/O block for an interface with a host CPU. It was fabricated using CMOS technology and has a chip of 2.6mm x 3.0mm in size that contains about 5,000 transistors. The driver/receiver circuit consists of one transistor, one capacitor and several resistors.