| 摘要 |
PURPOSE:To improve the transmission efficiency of a system, by transmitting a polling signal to each slave station with equal probability. CONSTITUTION:When a switching circuit 33 receives a selection-out signal selecting a lower-order slave station to be objective from a channel 11, one controller out of controllers 12 is selected with an output of a polling control circuit 23 to transmit the said selection-out signal. If a selection-in signal reporting that a specified lower-order device (slave station) does not exist, is transferred from the said selected controller, the selection-out signal is transmitted to other controllers 12 according to the output from the polling control circuit 23 again. This retrieval sequence is repeated until the selection of objective controller is successful or the polling of the entire controllers is finished. |
