| 摘要 |
PURPOSE:To prevent malfunction by running software as if a command were directly inputted to an alternative master station and further running software for the alternative master station. CONSTITUTION:Since a command execution part 120 equals a connection arrangement table in a master station 10 and that in the alternative master station 11, it instructs the alternative master station 11 to modify the connection arangement table through a link packet transmitting mechanism 140. The alternative master station 11 receives the modification instruction from the master station 10 by a link packet receiving mechanism 241, and transmits it to a command execution part 220. After the station 11 gives instructions that the connection arrangement table is modified to a table modifying mechanism 230, the modification ends. Then said mechanism 230 returns a message that the modification completely ends to the master station 11 through the link packet transmitting mechanism 240. Thus the identity of the connection arrangement table in the master station 10 and that in the alternative master station ll can be guaranteed, and a LAN can be run with the same arrangement even if the master station 10 brakes down to replace it with the alternative master station.
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