APPENDICES
Appendix 1 Precautions for Accessing Redundant CPU System
App
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DEVICE MONIT
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PROGRAMMING
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PENDICES
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INDEX
<When system switching occurs due to standby system error>
POINT
• Path switching is not executed when a communication to the Redundant CPU
specified at Logical station No. is faulty at communication start
*1
(A
communication error occurs.)
When a communication is faulty, refer to (4)(b) Checking method of path
switching occurrence and access examples of path switching in this section and
clear the communication disturbance.
*1: First communication after execution of the mdOpen function in the MELSEC data link library
(communications using the mdReceiveEx, mdSendEx, mdDevRstEx, mdDevSetEx, mdRandREx,
mdRandWEx, mdReceive, mdSend, mdControl, mdDevRst, MdDevSet, mdRandR. mdRandW or
mdTypeRead function).
• If other station access (including the programmable controller CPU other than the
Redundant CPU) is made to 257 or more stations simultaneously, communication
path may not be automatically switched.
Figure 2 Path switching example 2
Tracking cable
Tracking cable
Standby system
error
Connection to the
control system
Connection to the
control system
MELSECNET/H
CC-Link IE Controller Network
MELSECNET/H
CC-Link IE Controller Network
MELSECNET/H module
CC-Link IE Controller Network module
MELSECNET/H module
CC-Link IE Controller Network module
Personal computer
(CC-Link IE Controller
Network board)
Personal computer
(CC-Link IE Controller
Network board)
Control system
Standby system
Control system
Standby system
