System Switching Request Function Of Control System - Mitsubishi Electric MELSEC Q Series Reference Manual

7 APPLICATION FUNCTIONS

7.11.3 System switching request function of control system

Multiplexed remote master station
Multiplexed remote master station
Multiplexed remote master station
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The control system includes the system switching request function, i.e., the master
module mounted in the control system CPU issues the system switching request to the
control system CPU when it detects the data link error such as link cable disconnection
or communication error. This function enables the standby system to continue the
control even when the master module of the control system goes down.
System switching due to network error
Control system
Power QnPRHCPU QJ71
supply LP21
Error notice
Tracking cable
Link cable
A disconnection has occurred
(sub-master operation)
Standby system
Power QnPRHCPU QJ71
supply LP21
System A
However, if the CPU of the control system cannot perform system switching due to the
standby system error, only the master operation of the master module shifts to the
master module of the standby system (multiplexed remote sub-master station).
In this case, since the CPU of the standby system cannot process the sequence
program, the CPU controls the network only. (Various modules mounted in remote I/O
stations cannot be controlled.)
(sub-master operation)
Control system
Power QnPRHCPU QJ71
supply LP21
System A
Multiplexed remote sub-master station
Standby system
Power QnPRHCPU QJ71
supply LP21
System B
Multiplexed remote sub-master station
(master operation)
Control system
Power QnPRHCPU QJ71
supply LP21
System B
Multiplexed remote sub-master station
(master operation)
Standby system
QnPRHCPU QJ71
Power
supply LP21
System B
Under an error
MELSEC-Q
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