Mitsubishi Electric Melsec QJ71LP21 Reference Manual page 359

7 APPLICATION FUNCTIONS
[When the redundant system is in normal communication]
Redundant system
Station No. 1 Station No. 2
(control system) (standby system)
Host station
send range
Tracking
Station No. 3 Station No. 3
Received data Received data
Station No. 4 Station No. 4
Received data Received data
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(b) Sending and receiving cyclic data
Cyclic data are sent and received by the following processing:
1) Processing by the network module connected to the control system
The redundant system consists of a control system and a standby
system, and only the control system executes programs. Thus, the
network module connected to the control system sends and receives
cyclic data.
2) Processing by the network module connected to the standby system
The network module connected to the standby system only receives
cyclic data from other stations to continue control when system
switching results from either of the following events.
For details of system switching, refer to the QnPRHCPU User's
Manual (Redundant System).
● System switching (control system's CPU module, network module,
or power supply module malfunction or error, etc.)
● Manual system switching (GX Developer, system switching
dedicated instructions, etc.)
Perform tracking from the control system CPU to the standby system
CPU using the host station send range as a tracking device.
To perform cyclic transmission in the redundant system, pairing must be set
in the network parameters.
For details of pairing setting, refer to Section 7.10.3.
Station No. 3 Station No. 4
Station No. 1 (2) Station No. 1 (2)
Received data Received data
Station No. 3
Host station
Received data
send range
Station No. 4 Host station
Received data send range
*1
[When station No. 1 is returned ]
Redundant system
Station No. 1 Station No. 2
(standby system) (control system)
Host station
send range
Tracking
Station No. 3 Station No. 3
Received data Received data
Station No. 4 Station No. 4
Received data Received data
*1: Even if the station is recovered from a communication error,
system switching does not occur in the redundant system.
[When station No. 1 is cut off due to a communication error (system switching occurs)]
Redundant system
Station No. 1 Station No. 2
(standby system) (control system)
Host station
Host station send range
send range
Station No. 3 Station No. 3
Received data Received data
Station No. 4 Station No. 4
Received data Received data
Station No. 3 Station No. 4
Station No. 1 (2) Station No. 1 (2)
Received data Received data
Station No. 3
Host station
send range Received data
Station No. 4 Host station
Received data send range
MELSEC-Q
Station No. 3 Station No. 4
Station No. 1 (2) Station No. 1 (2)
Received data Received data
Station No. 3
Host station
Received data
send range
Station No. 4 Host station
Received data send range
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