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Execution availability of system switching
The following tables show the execution availability of system switching.
: Switching possible, : Switching not possible
Status of system using the
SIL2 Process CPU
Normal operation or continuation
error in the standby system
Tracking communications
disabled (cable disconnection)
Power-off, reset, hardware
failure of the standby system
CPU module
Stop error in
WDT error
the standby
Error other
system
than WDT
error
Network error detected in the
*1
standby system
During memory copy from
control system to standby
system
During online change
Mismatch between the CPU
module operating status of both
systems
Mismatch between the safety
operation mode of both systems
Error in safety tracking data
detected
*7
During system switching
During online
Redundant
module
function
change
module
Other modules
System switching disabled by the
DCONTSW instruction
*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 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 the cause of the 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 the cause of the system
switching failure is returned.
*5 When the systems are switched during an online 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 644 File)
*6 Although the control system CPU module is switched to the standby system CPU module, the existing standby system is not switched.
*7 The initial processing of the safety function after system switching completes is also included.
37 FUNCTIONS
616
37.1 System Switching
Execution availability of system switching
Automatic system switching
Power-off or
Hardware
reset of the
failure of
CPU
the CPU
module
module
*6
*6
*6
*6
*6
Stop error of the CPU
module
WDT error
Error other
than WDT
error
*6
*6
*6
*6
*6
*6
*6
Manual system switching
System
System
switching
switching
request
request by
from a
the
network
SP.CONTSW
*3
*3
module
instruction
*2*5
System
switching
request
from the
engineering
*4
tool
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