Precautions - Mitsubishi Electric MELSEC iQ-R-R00CPU User Manual

Precautions

The following describes the precautions on system switching.
Item
Error in the redundant function module
When both systems operate as standby
systems
When both systems operate as control
systems
Scan time monitoring function
System switching disabled by online
change
Operation of an event execution type
program
When the cable for the network module is
disconnected
System switching during initial processing/
initial processing (when switched to RUN)
CC-Link control at system switching
Description
• When an error has been detected on the redundant function module, the control
system and standby system continue operating without being switched.
• When a communication error has been detected in the communication between
the redundant function module and a CPU module, the systems are switched.
• If a communication error has occurred due to a tracking cable error during system
switching, both systems may operate as standby systems.
• If a WDT error or a hardware failure of the CPU module has occurred in the control
system while a stop error exists in the standby system, both systems operate as
standby systems.
If the tracking cable and the network cable that is connected to the control system
network module are simultaneously pulled out or disconnected, both systems may
operate as control systems.
In this case, connect the tracking cable again. After a stop error has occurred in the
system B, power off and on or reset the system B.
During system switching, scan time monitoring with the watchdog timer is interrupted.
Thus, in a scan in which the systems are switched, no error is detected even if the
scan time monitoring time has elapsed.
A time taken for system switching does not need to be considered in the scan time
monitoring time (WDT) setting.
In a redundant system, the manual system switching is disabled during an online
change.
When "ON of bit data (TRUE)" has been specified in the trigger type and the systems
are switched before tracking transfer of device data, an event execution type
program does not operate in the new control system.
If a network module cable is disconnected, the systems may not be switched
depending on the timing of error detection on the control system and the timing on
the standby system.
• When a system switching cause has been generated during initial processing or
initial processing (when switched to RUN) on the control system, the systems are
switched after the initial processing or initial processing (when switched to RUN).
• When a system switching cause has been generated during initial processing or
initial processing (when switched to RUN) on the standby system, whether the
systems are switched or not depends on the system switching cause.
When the master operating station is switched with a program by using the CC-Link
standby master function, the CC-Link control can be continued even after system
switching.
Reference
Page 452 Error in the
redundant function
module
Page 452 When both
systems operate as
standby systems


Page 452 System
switching disabled by
online change

Page 453 When the
cable for the network
module is disconnected
Page 453 System
switching during initial
processing/initial
processing (when
switched to RUN)
MELSEC iQ-R CC-Link
System Master/Local
Module User's Manual
(Application)
28 FUNCTIONS
451
28.2 System Switching
28