Functions restricted in a redundant system
Functions with restrictions when communicating with a redundant system over Ethernet are as follows.
When performing the re-initial processing, specify "0H" for the modification specification (S+2) in the control data of the UINI
instruction to execute the instruction.
■Communications using TCP/IP
Set the Ethernet-equipped module side as Passive open and perform the open/close processing from the external device
side. When Active open is performed from the Ethernet-equipped module side, if system switching occurs before execution of
the close processing from the Ethernet-equipped module side, the close processing may become unexecutable.
■Communication using the SLMP and communications using the random access buffer
When communicating with the standby system using user connection, set "Do Not Open by Program" for "Opening Method" in
"Own Node Settings" under "Basic Settings".
■When the network type is "Q Compatible Ethernet"
For the standby system CPU module, the open/close processing by input/output signals cannot be performed.
Direct connection with MELSOFT products and a GOT
When the network type is "Q Compatible Ethernet", execute direct connection with the engineering tool either using the CPU
module (built-in Ethernet port part) or after setting "Disable" for "System Switching Request Issuing at Disconnection
Detection" in "Redundant System Settings" under "Application Settings".
When "Enable" is set for "System Switching Request Issuing at Disconnection Detection", if a cable is disconnected after a
direct connection with the engineering tool is made, system switching will occur.
Searching the CPU module on the network
Even with the control system IP address set, when a CPU module search is performed, the control system IP address is not
displayed. The IP addresses of systems A and B are displayed.
Communications using the SLMP
For the request message, set 00H to the request destination network number and FFH to the request destination station
■Access to the control system, standby system, and systems A and B
For SLMP communications, using the command request destination module I/O number, the control system CPU, standby
system CPU, system A CPU, or system B CPU can be specified as the access destination.
By specifying the access destination CPU module, even if system switching occurs due to a communication error, access to
the specified CPU module is possible using the communications path bypass function. For details on the request destination
module I/O number, refer to the following.
SLMP Reference Manual
■When accessing other stations via a redundant system
When accessing other stations by dynamic routing via a redundant system on the same Ethernet, access via the control
system. An error occurs if accessing via the standby system.
When accessing other stations via the standby system on the same Ethernet, set "Routing Setting" of "CPU Parameter".
1.17 Redundant System Function