Is there a good functional reason to add two PLC connections to separate Leased and Driven tags?

Ignition
1

I am looking at a customer's setup and they separated PLC connections based off the type of tag they are pulling from it. I am scratching my head as to why they would do this setup when they could just make two tag providers to accomplish the same thing.

Am I crazy or is this unnecessary? Wouldn't this add unnecessary overhead to the gateway?

The connections list looks like the following:

PLC_A_Leased
PLC_A_Driven
PLC_B_Leased
PLC_B_Driven
PLC_C_Leased
PLC_C_Driven
2

This is done so that re-optimization due to lease changes doesn't effect the non-leased tags.

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3

Thanks, your answer helped me find more information about it.

4

This is not an issue with my drivers, FWIW.

The lease killer is this:

I know Kevin plans a fix, but there no timeline that I know of.

5

This behavior changed in 8.3 for the better.

There’s still an issue with the Logix driver’s heavy-handed approach to re-optimizing every time subscriptions change.

I’m testing a new approach to managing sampling that should be more friendly to lease changes with the Beckhoff ADS driver. If it works out, future drivers, including some future Logix driver rewrite, will probably use a similar approach.

3 Likes