| 摘要 |
PURPOSE:To simplify determination at the time of polling command transmission by providing the receivable number of blocks into a polling command on a data communication system with its primary station connected to several secondary station in a series loop and by judging states of secondary stations from this number of blocks. CONSTITUTION:In this loop transmission system, primary station 2 is connected to several secondary stations 3 to 12 in a series loop, and group polling is made from primary station 2 to all of secondary stations 3 to 12 or a fixed secondary station in order to transfer data from assigned secondary stations 3 to 12 to primary station 2. In addition, primary station 2 displays a fixed registered number in a polling command. Then, assigned secondary stations 3 to 12 send out data blocks of their stations through loop 1 and also transfer the sums of or the difference between fixed registered numbers in commands and the numbers of data blocks of their stations to primary station 2, which detects the registered numbers, thereby determining the period for the control of repolling. |
