| 摘要 |
PURPOSE:To make processings simple to make it possible to cope with change and extension easily, by providing one set for transmission and receiving of buffers for frame sequence number storage in each station in the N-to-M loop transmission system. CONSTITUTION:Information devices ID1-IDn are connected into a loop through transmission line TL by transmission stations ST1-STn, and each transmission station is provided with transmission sequence counter SCC and receiving sequence number register RSNR. The transmission station which has obtained the line occupation right sets sequence number SN to 0 first to perform frame transmission and adds 1 to transmission SN each time a frame is transmitted. The station which is designated as a receiving station compares received transmission SN with SN stored in RSNR by comparator COMP1; and when they agree with each other, signal SNOK indicating the SN has been detected normally is obtained. The value obtained by adding 1 to the value of received transmission SN is stored in RSNR as receiving SN together with the transmission station address. When it is detected that the transmission station has abandoned the line occupation, receiving SN is reset to zero. |
