Mitsubishi MELSEC-A Series Reference Manual page 227

8. PROCEDURES TO OPERATION
(3)
(4)
The station numbers in the same loop have to be all different.
If the same station number is assigned to another station in the same loop, the link
module closer to the receiving port of the master station is applied, and the link data
in the other station is ignored. Therefore, the setting as Fig 8.4 cannot be made.
Fig 8.4 When setting the same station number
When the number of slave stations set with link parameter differs from the actual
number of slave stations
(a) When the set number of slave stations is greater than the actual number of slave
stations, the slave stations do not exist in the system are treated as
communication faulty stations.
(b) If the set number of slave stations is less than the actual number of slave
stations, the data link is only performed to the slave stations set with the link
parameters.
All other slave stations are processed as off-line mode stations.
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