| 摘要 |
A network manager, when a transmission is requested from any FA equipment under control by the network manager, sets a flag indicating a loop direction for transmission in a transmission frame and transmits the transmission frame to other stations, and when network controllers receive the transmission frame with a flag indicating the loop direction set therein, the network controllers check whether the loop through which the transmission frame was actually received is the same as that indicated by the flag in the received transmission frame or not, and if it is determined that the loop through which the transmission frame was actually received is different from that indicated by the flag above, the network controllers send the transmission frame including an error report indicating the loop direction to the network manager.
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