| 摘要 |
PURPOSE:To transmit protective information in 1:n time division transmission by executing the formation of a transmission code and the test of a receiving code by opposed two I/O control circuits and transmitting the transmission code reversedly synchronously with 1:n transmission cycle or executing the reverse transmission every cycle. CONSTITUTION:When a poling code is transferred from a transmission control circuit 1 to an I/O control circuit 3, a maintenance code CS1 for a controlled device S1 is formed and returned from the circuit 3 to the circuit 1. When the code CS1 is transmitted from the circuit 1 to the device S1, transmission control circuits 2 of the devices S1-Sn receive the code CS1, and at the completion of the reception, only the device S1 concerned transfers the code CS1 to its I/O control circuit 4. The circuit 4 inputs the code CS1 and transfers a maintenance code S1C for the control device C to the circuit and the circuit 2 transmits the code S1C through a transmission line 6. After receiving the code S1C, the circuit 1 transfers the code S1C to the circuit 3 to end the transmission cycle S1Y. Consequently, transmission can be reversed every cycle.
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