Mitsubishi Electric MELSEC SW1DNC-CCIEF-B User Manual page 181

Checking method of path switching occurrence
When the system is communicating with the redundant CPU specification, whether communication is continued by path
switching due to communication error occurrence can be estimated.
Create a program that monitors the following special relay and special registers to check the occurrence of path switching.
<Special relay and special registers to be monitored and estimated possibility of path switching>
*1 *2
SM1600 SD1590
OFF Either one is other than 0
ON 0
ON Either one is other than 0
*1 Even if SM1600 is ON, path switching does not occur when the CPU is not accessed via the tracking cable.
*2 When using SM1600, SD1590, and SD1690 to estimate the occurrence of path switching for the Redundant CPU connected via
MELSECNET/H, check the following items on the Redundant settings in the network parameter of GX Developer.
Issue system switch in Cable disconnection timeout
Issue system switch in communication error
Check the following based on the statuses of the above special relay and special registers, and remove the error cause.
• Check the Redundant CPU for an error.
• Check the tracking cable status and whether the tracking cable is correctly connected.
• Check both the relevant network module and the network where that relevant network module is connected for an error.
Access examples of path switching
The following shows examples of path switching during access to the control system.
<Figure 1 When system switching occurs due to communication error>
CC-Link IE Field Network
Connection to the
control system
Personal computer
(CC-Link IE Field
Network board)
CC-Link IE Field Network
Connection to the
control system
Personal computer
(CC-Link IE Field
Network board)
*2
SD1690 Possibility of path switching
Since a system switching request from the network module was detected, path
switching may have been executed.
0 Since another system error occurred, path switching may have been executed.
Since another system error occurred or a system switching request from the
network module was detected, path switching may have been executed.
CC-Link IE Field Network module
MELSECNET/H module
MELSECNET/H
Communication
Control system
CC-Link IE Field Network module
MELSECNET/H module
MELSECNET/H
Standby system
error
Standby system
Tracking cable
Control system
Tracking cable
Appendix 1 Precautions for Accessing Redundant CPU System
Reference
Page 179 Access
examples of path
switching
Figure 1
Page 179 Access
examples of path
switching
Figure 2
Page 179 Access
examples of path
switching
Figure 1, Figure 2
A
APPX
179