5
- 37
5.3 The System Switching Function
5.3.1 System Switching Method
5
POINT
1. The network module system switching can only be requested from a
redundant system-compatible CC-Link IE Controller Network module,
MELSECNET/H module, Ethernet module, and PROFIBUS-DP master
module.
Refer to Section 2.3 for details on serial Nos. of these redundant system-
compatible modules.
2. When the Ethernet module is mounted on the extension base unit, the system
switching request cannot be issued.
(The CC-Link IE Controller Network module and MELSECNET/H module
cannot be mounted on the extension base unit.)
If the network module cable is disconnected, the system switching may not be
performed depending on the timing when the control system and standby system
detects the fault.
Example: The following diagram shows the processes that take place when
the redundant system is connected to the MELSECNET/H.
• If the control system detects the cable disconnection first, the system
switching will be performed.
• If the standby system detects the cable disconnection first, the system
switching will not be performed.
• In this case, the "CAN'T SWITCH (error code: 6220)" continuation error will
occur in the control system CPU module.
Diagram 5.25 System Switching Operation at Cable Disconnection
System A
System B
Control system
System switching
request
Standby system
Error detection
Other Station's system
MELSECNET/H
2) Cable severed
(System A and B are
standalone)
1) Cable severed
(QnPRH system
only is standalone)
