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

Precautions

The following table lists 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
When a stop error is generated in a
new standby system 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 is generated 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.
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.
When executing a system switching, if there is a hardware failure in the SIL2 Process
CPU or SIL2 function module, the startup of the safety control after switching to the
new standby system may take two seconds longer compared to the normal system
switching.
Reference
Page 620 Error in the
redundant function module
Page 620 When both
systems operate as standby
systems


Page 620 System switching
disabled by online change

Page 621 When the cable for
the network module is
disconnected
Page 621 System switching
during initial processing/initial
processing (when switched to
RUN)
MELSEC iQ-R CC-Link
System Master/Local Module
User's Manual (Application)

37 FUNCTIONS
619
37.1 System Switching
37