Abstract: In a method of controlling the start of data communication between two LSIs (master and slave) effecting a ping-pong transmission and the configuration of those LSIs, both the master and slave LSIs receive and detect a start instruction signal before starting the data transmission. The master LSI transmits an answer signal upon receiving a start instruction signal from the slave LSI, and starts, after a prescribed period of time, the ping-pong transmission to the slave SLI. In addition, when the master LSI itself transmits a start instruction signal to the slave LSI, it serves to start the ping-pong transmission to the slave LSI after receiving the answer signal from the slave LSI. The slave LSI transmits back, upon receiving the start instruction signal from the master LSI, an answer signal to start the ping-pong transmission.

Abstract: An equalizer circuit for equalizing a signal attenuated in frequency while the same is transmitted through a transmission line and eliminates out-band high frequency noise so as to provide a signal having flat frequency characteristics. The equalizing circuit includes a high-pass circuit, a Sallen-Key low-pass circuit capable of gain regulation, constructed by connecting the output terminal of an operational amplifier through a resistance to the negative input terminal of the same and grounding the negative input terminal through a variable resistance, an amplifying circuit capable of gain control for amplifying a signal supplied to the positive input terminal of the operational amplifier of the Sallen-Key low-pass circuit, and a control circuit which detects the peak level of the output signal of the amplifying circuit and controls the resistance of the variable resistance of the Sallen-Key low-pass circuit and the gain of the amplifying circuit on the basis of the result of the detection.