Mitsubishi MELSEC-A Series Reference Manual page 226

8. PROCEDURES TO OPERATION
Precautions for setting the link module station numbers
The following shows the precautions for station number setting.
(1)
(2)
Station numbers have to be consecutive.
Station numbers cannot be skipped as Fig 8.2.
If station numbers are not set consecutively, the time taken for the system to switch to
the loopback mode when the slave station is powered off is increased.
Therefore, the loopback processing is not performed within the monitoring time set in
link parameter, which may cause the entire data link system to stop.
Fig 8.2 When not setting station numbers consecutively
Station numbers have to be set in ascending order.
Station numbers cannot be set in descending order as Fig 8.3.
Fig 8.3 When setting station numbers in descending order
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