Mitsubishi Electric MELSEC iQ-R Series - Execution Availability of System Switching

26 REDUNDANT FUNCTION
26.2 System Switching
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Execution availability of system switching
The following tables show the execution availability of system switching in each operation mode.
In backup mode
: Switching possible, : Switching not possible
*1 When the group specification has been set in the standby system, a network error is not detected if communication is available with the
line of an Ethernet-equipped module after a communication error has occurred on the other Ethernet-equipped module. ( MELSEC
iQ-R Ethernet User's Manual (Application))
*2 After the online change has been completed, the system switching cause is detected and the systems are switched. However, when an
online program change is being executed only in the standby system, the systems cannot be switched.
*3 If system switching is disabled when a system switching request is sent, a continuation error occurs and a cause of a system switching
failure is stored in SD1644 (Cause of system switching failure).
*4 If system switching is disabled when a system switching request is sent, the error code corresponding to a cause of the system
switching failure is returned.
*5 When the systems are switched during an online program change, a mismatch between the files is detected in the system consistency
check and a stop error may occur on the new standby system. ( Page 415 Files)
*6 Although the CPU module of the control system is switched to the standby system, the current standby system is not switched.
Redundant system status Execution availability of system switching
Automatic system switching Manual system switching
Power-off
or reset of
the CPU
module
Hardware
failure of
the CPU
module
Stop error of the
CPU module
System
switching
request from
a network
module
*3
System switching
request by the
SP.CONTSW
instruction
*3
System
switching
request from
the engineering
tool
*4
WDT
error
Error other
than WDT
error
Normal operation or continuation
error in the standby system
   
Tracking communications disabled
(cable disconnection)

*6

*6
  
Power-off, reset, hardware failure of
the CPU module of the standby
system

*6

*6
  
Stop error in
the standby
system
WDT error 
*6

*6
  
Error other than WDT
error

*6
  
Network error detected in the standby
system
*1
   
During memory copy from control
system to standby system

*6
  
During online program change  
*2*5

Operating status mismatch of the
CPU modules in both systems
   
During system switching    
During online
module
change
Redundant function
module

*6

*6
  
Module on the main
base unit in a
redundant system
with redundant
extension base unit
   
Other modules    
System switching disabled by the
DCONTSW instruction
   