Patent ID: 7743273

Claim:
A serial communication system, comprising: a first unit including a master microcomputer that includes a clock signal output port that outputs a clock signal, and a synchronous data transmission port that transmits data in synchronization with the clock signal; a second unit including a slave microcomputer that includes a clock signal input port to which the clock signal in input, and a synchronous data receiving port that receives the data transmitted from the synchronous data transmission port in synchronization with the clock signal; wherein: the master microcomputer includes a first function switching port whose function is selectively set to one of a first receiving function that receives the data in synchronization with the clock signal, and a first transmission function that transmits a signal asynchronously to the clock signal; the slave microcomputer includes a second function switching port whose function is selectively set to one of a second transmission function that transmits the data in synchronization with the clock signal, and a second receiving function that receives the asynchronous signal; in a first operation mode in which the data is transmitted and received between the first unit and the second unit, the data is transmitted from the synchronous data transmission port to the synchronous data receiving port, and the data is transmitted from the second function switching port whose function is set to the second transmission function, to the first function switching port whose function is set to the first receiving function; and in a second operation mode in which the first unit transmits the data to the second unit at a higher transmission speed, and the asynchronous signal is transmitted from the first function switching port whose function is set to the first transmission function, to the second function switching port whose function is set to the second receiving function.