System Switching Request Function Of Control System - Mitsubishi QJ71LP21 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
7 - 39
The control system includes the system switching request function, i.e., the network
module mounted in the control system issues the system switching request to the
QnPRHCPU 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 network module of the control system goes down.
System switching due to network error
Control system
QnPRHCPU QJ71
Power
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 QnPRHCPU of the control system cannot perform system switching
due to the standby system error, only the master operation of the network module
shifts to the network module of the standby system (multiplexed remote sub-master
station).
In this case, since the QnPRHCPU 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
QnPRHCPU QJ71
Power
supply LP21
System A
REMARK
For the details of system switching, refer to QnPRHCPU User's Manual (Redundant
System).
Multiplexed remote sub-master station
Standby system
QnPRHCPU QJ71
Power
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
LP21
supply
System B
Under an error
MELSEC-Q
7 - 39