Hitachi, Ltd.

Kenitiro Takahashi

Yukichi Ueno

In a communication network in which a main station and several I/O systems are connected by a closed-loop communication line, the communication line includes a data channel and a clock pulse channel extending in parallel with the data channel. Predetermined data bit lengths are allotted to the individual I/O systems. A train of clock pulses, the number of which is equal to the sum of the data bit lengths alloted to the I/O systems, is supplied from the main station to the I/O systems, and data arranged in the order of reception by the I/O systems are transmitted from the main station to the I/O systems in synchronism with the clock pulses. In each of a number of I/O systems, the clock pulses, corresponding to the number of data bits allotted to the particular station, is counted to fetch the data supplied while the clock pulses are being counted. At the same time, the I/O system sends out data generated therein toward the main station while the clock pulses are being counted. In the other period of time, data and clock pulses supplied to that I/O system are transferred intact to the I/O system in the next stage.

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Ibaraki, Japan

Kenitiro Takahashi