APPENDICES
Appendix 1 Precautions for Accessing Redundant CPU System
App
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DEVICE MONIT
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MELS
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BRAR
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PROGRAMMING
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AP
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FUNCT
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ROR COD
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TROU
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PENDICES
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INDEX
(b) Checking method of path switching occurrence and access examples of path
switching
1) Checking method of path switching occurrence
When the system is communicating with the redundant system specified,
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: 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.
SM1600
*1
SD1590
*2
SD1690
*2
Possibility of path switching
Reference
OFF
Either one is other than 0
Since a system switching request from the network module
was detected, path switching may have been executed.
ON
0
0
Since other system error occurred, path switching may have
been executed.
ON
Either one is other than 0
Since other system error occurred or a system switching
request from the network module was detected, path
switching may have been executed.
