1 FUNCTIONS
1.17 Redundant System Function
221
1
System switching request to the control system CPU module
This function issues a system switching request to the control system CPU module if the RJ71EN71 mounted on the control
system in a redundant system detects a communication error or cable disconnection.
However, depending on the operating status of the standby system, system switching is not executed.
For details on the operating status of the standby system and whether system switching is executable, refer to the following.
MELSEC iQ-R CPU Module User's Manual (Application)
The CPU module (built-in Ethernet port part) cannot issue a system switching request.
System switching cause
This section describes causes that make the RJ71EN71 issue a system switching request. Whether to issue a system
switching request due to each cause is set in "Redundant System Settings" under "Application Settings". ( Page 276
Redundant System Settings)
In the following cases, system switching is not performed even if the RJ71EN71 issues a system switching
request.
• When the other RJ71EN71 in the redundant module group is operating normally ( Page 223 Redundant
module group settings)
• When the other port in the port group is operating normally ( Page 224 Port group setting)
For details on causes other than a system switching request from the RJ71EN71, refer to the following.
MELSEC iQ-R CPU Module User's Manual (Application)
Moderate/major error and hardware failure
When detecting an error where the module cannot continue the processing, the RJ71EN71 notifies the control system CPU
module about the error and issues a system switching request.
Communication error detection
Set connections targeted by communication error detection in "Redundant System Settings" under "Application Settings".
( Page 276 Redundant System Settings)
The following connections can be set as targets of communication error monitoring.
• User connections
• Auto-open UDP port
• FTP transmission port (TCP/IP)
• MELSOFT transmission port (TCP/IP)
• MELSOFT transmission port (UDP/IP)
■Existence confirmation
When the RJ71EN71 has not communicated with the external device for a certain period of time while the connection is open,
this function checks whether the external device is alive. ( Page 246 Existence Confirmation)
When no response is returned from the external device, the Ethernet-equipped module closes the relevant connection and
issues a system switching request to the control system CPU module.
System switching cause Description
Moderate/major error and hardware failure An error where the RJ71EN71 cannot continue the processing was detected
Communication
error detection
Existence
confirmation
After a connection is opened (open processing), the existence of the external device cannot be checked.
ULP timeout An ACK response is not returned from the external device within the TCP ULP timer time.
Disconnection detection The Ethernet cable connected to the RJ71EN71 was disconnected.
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