800XA 5.1 Ac800M redundancy fail

I have one AC800M PM861 in redundant configuration.

when i disconneth both ethernet networks cables in primary CPU I suppose CPU toggle automatically to dual, but it does not work,

it is necesary to fix some settings to have this working fine?

By csanchez411 on 5/10/2018 | Like (0) | Report

Thanks for your response, now the redundancy toggle works, when both ethernet cables are unplug, but the secondary CPU entre in fail state, we connect cables again , but fails persist, it is necesary to do one reset backup.
and the CPU restart and syncronize again.

By kstoilov on 5/12/2018 | Like (0) | Report

As I know, that is right. You have to reset the backup CPU manually after that

By kstoilov on 5/12/2018 | Like (0) | Report

I don't know a way for automatic restart after switchover - that is described in the manual:
Following a changeover, the system operates as a system without redundancy with only one processor unit in operation. You can replace the malfunctioning processor
unit while the system is running. After the replacement is carried out, the system once again has a redundant processor unit

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asked 14 days ago



Processor unit redundancy is available for PM861, PM864, PM865, PM866, and PM891. In this case, the controller contains two processor units, each including memory for system and application software. One unit is acting as primary, the other is backup (hot stand-by). The primary processor unit controls the process. The backup stands by, ready to take over in case of a fault in the primary. The changeover is done bumplessly and in less than 10 ms. During the changeover, the process outputs are frozen.

I don't think this is a valid CPU redundancy test.

Please refer to "Verification of Redundant CPU" section from AC800M Controller Hardware documentation.


answered 14 days ago


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Are the controllers configured correctly? Before pulling cables, I would check:

- Redundant unit added in CBM

- IP addresses configured in using IP Config tool

- Hardware all present and correct (redundant link cable and BC810, if used)

- Dual light present on both controllers


answered 14 days ago


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You didn't present enough data for configuration and connection of your redundant CPU's.

Anyhow, if both CN1 and CN2 on the primary CPU's are disconnected, it have to switch-over to the backup CPU.

Details for configuration of redundant CPU's and automatic switch-over are described in manuals, for example 3BSE036351R5001 or similar.

One of possible reasons for automatic switch-over is:

"Severe communication errors on the Control network, that is, loss of both network ports in the Primary CPU"

I could recommend you to proceed with configuration of both CPU's and CN1/2 as described. You have to do both IPConfig and Config in CBM.

Also, backup CPU have to be "operational" and connected to the control netwrok and IO system (same as primary). The first test should be in Online mode from CBM - try to switch-over from primary to backup CPU and ensure if backup CPU will take control. Then proceed with other tests.

I have tested automation switch-over with PM861 when both CN1/2 are disconnected in primary CPU and it works.

Source: 3BSE036351R5001


answered 14 days ago


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I did tested it in my lab, it works fine.

After disconnecting the primay and secondary network cable, the primary CPU restarts and the secondary CPU takes over.

Please check you redundant CPU configuration and IP configuration.


answered 14 days ago


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Similar discussion for a redundant system with no network redundancy





answered 13 days ago


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Did you proplery set up the Redundant Controller IP configuration when assigning the IP address for CN1 in the IPconfig tool. Normally this is done to use the default rules, See attached Screenshot:


answered 12 days ago


By csanchez411 on 5/11/2018 | Like (0) | Report

Thanks, yes we follow this instructions, and now redundancy works, but secondary CPU enter in fail mode, and it is necesary to reset manually.

By csanchez411 on 5/11/2018 | Like (0) | Report

Thanks, yes we follow this instructions, and now redundancy works, but secondary CPU enter in fail mode, and it is necesary to reset manually.

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