When Switching to Redundancy Option Kit Backup Controller, the Backup Controller May Post Errors or Reset

Applies To:

SNAP-PAC-ROK
SNAP-PAC-S1, SNAP-PAC-S1-FM, SNAP-PAC-S1-W
SNAP-PAC-S2, SNAP-PAC-S2-W

Versions Affected:

R9.0a through R10.0d

Symptoms:

In a system with the SNAP PAC Redundancy Option Kit, if the PAC Control strategy utilizes non-persistent pointer variables or pointer tables, the strategy will run normally on the primary controller, until it switches to the backup controller. Because non-persistent pointers are not propagated to the backup controller, when the backup controller becomes active and it attempts to use one of the pointers or pointer table elements, the pointer or pointer table element may contain an invalid value. In that case, the backup controller may post errors or even reset.

Workaround:

Make sure that you initialize any non-persistent pointers (for example, use the Move to Pointer command) in the logic after each sync block. This is necessary because when there is a switch to the backup controller, the logic can start at any Sync block, so you can't rely on previous logic to initialize the pointer variable.

Resolution:

Opto 22 is investigating this issue.

Questions?

Contact: Opto 22 Product Support.
Phone: 800-835-6786 or 951-695-3080
Email: support@opto22.com

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