| 摘要 |
PURPOSE:To attain efficient polling by increasing a polling period to a terminal device having no response when there exists said terminal device in the polling from a controller side until the next response is obtained. CONSTITUTION:A terminal number counter 8 and non-response counters 91-9n are brought to the initial state. Then, the non-response counter 91 of the 1st terminal device performing the polling is observed and it is confirmed that the content is zero, a predetermined time is set to a monitor timer 7 and a polling command is transmitted to said terminal device. When the response from the terminal device returns in the time set to the monitor timer 7, data are transferred with the terminal device. In this case, when the response from a terminal device transmitting the polling command does not return, the corresponding non- response counter is incremented by one while the time set to the monitor timer 7 is in timeout. Further, the terminal number counter 8 is revised and the system enters the polling control of the next terminal device. |
