| 摘要 |
<p>PROBLEM TO BE SOLVED: To achieve system redundancy with a simple structure.SOLUTION: A lower-level device 101 for communicating with an upper-level device includes: a port switchover control unit 32 capable of setting one of a first port and a second port, which inputs and outputs communication signals between with another device, to be a master port, and setting another port to be a slave port; and a communication control unit 31 for performing processing to establish a communication connection with the other device through the first and second ports. When the communication connection with the upper-level device or another lower-level device 101 cannot be established through the slave port, the port switchover control unit 32 performs switchover processing between the master port and the slave port. On completion of the switchover processing by the port switchover control unit 32, the communication control unit 31 performs processing to establish a communication connection with the upper-level device or the other lower-level device 101 through the slave port after the switchover.</p> |
