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MELSEC-Q
7 APPLICATION FUNCTIONS
(b) Cyclic transmission
Station No. 4
Host station
send range
Station No. 1 (2)
Received data
Received data
Station No. 3
Host station
send range
Station No. 3
Received data
Station No. 4
Received data
Station No. 3
Received data
Station No. 4
Received data
Station No. 3
Host station
send range
Station No. 1 (2)
Received data
Station No. 4
Received data
Redundant system
2)
2)
0000
H
00FFH
0100
H
01FFH
0200
H
02FF
H
1)
1)
Host station
send range
1) Station No. 2 takes over the host station send range data handled by station No. 1 (data tracked)
and sends them to other stations without discontinuing a data link.
2) Station No. 2 receives data from other stations.
[When station No. 1 is cut off due to a communication error (system switching occurs)]
If a communication error occurs in station No. 1 and it is consequently cut off from the network, the network module automatically
issues a system switching request to the control system CPU, and system switching occurs in the redundant system.
After system switching, station No. 2, a new control system, continues a data link.
Cyclic transmission after system switching in the redundant system is shown below.
Station No. 2
(control system)
Station No. 1
(standby system)
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