SLC 5/04 via ControlLogix Bridge Communication Performance Tips?

[witman]

Are there any tips/tricks to get the best communications performance with an SLC 5/04 connected to Ignition via DH±->DHRIO–>ENBT/A? There are also a couple very old RSView HMIs on the DH+ network. There used to be more on it, but we’ve moved everything else off DH+.

We are gradually migrating from RSView to Ignition on this system and are now reading a lot of tags in Ignition.Presently, these are setup in a direct scan class at one second. Lately we’re noticing a few performance issues with the SLC 5/04 (does not affect other PLCs connected to Ignition):
1 - Some tags can take quite a while to show good quality when opening a new window
2 - Communication with SLC 5/04 via RSLogix 500 is slow (obvious when uploading values before save)
3 - RSLogix 500 has difficulty connecting to / staying connected to the SLC

In Ignition 7.9.8, the status page for this device is not very enlightening with status: “Hello world”

Any suggestions/guidelines before playing with scan class(es)?

[pturmel]

You're kind of toast. By default, DH+ is only 57kbits/second. If all of your hardware is compatible, you can select 230k, but it is still a tiny fraction of the bandwidth available to the slowest ethernet processor. RSLogix is a bandwidth hog -- any programming activity will crush your comms.
A short-term fix for some would be to swap the 5/04 for a 5/05, using the DHRIO bridge in the Logix chassis to maintain messaging access from the DH+ devices to the new Ethernet devices. When you do that, do check your comm throttles in your status file:

Typical Performance between Ignition and AB SLC 5/05

Check “Comms Servicing Selection” and “MSG Servicing Selection” for channel 1 (S:2/15 & S:33/7). If either is set, it will crush your throughput, as only one request will be processed per scan (Comms) or per certain control flow instructions (MSG).

[witman]

Thanks Phil. I suspected we would hit this wall eventually.

[witman]

Update: After replacing all the other DH+ devices with Ignition so only the SLC 5/04 with 64K was left, the ENBT/A died and we replaced the SLC 5/04 with a 5/05 to completely eliminate DH+ (and ControlLogix bridge).

On the SLC 5/04, we got tag updates down to 1 s (from ~2.5 s) without overload by adding multiple SVC instructions in addition to setting the flags @pturmel notes. One SVC instruction helped, and adding more between large sections of code helped more.

Typical Performance between Ignition and AB SLC 5/05

I can confirm this solution worked for me as well. Clearing S:2/15 and S:33/7 yielded minor increases in performance but adding a SVC decreased my overload from 170% to 60% for a 600ms tag group

It's still an obsolete PLC, but less obsolete now. It looks sad next to Beckhoff PLCs and Ignition HMIs breezing along at 10 updates per second, but is comparable to Ignition HMIs using remote tag providers that are artificially limited to updating once per second. Hopefully that remote tag provider update limit becomes configurable at some future point:

Remote Tag Provider updates tags slower than Realtime Tag Provider

@Kevin.Herron, batching makes sense. However 1000 ms feels really slow. What are the chances we could get a setting for this, or get the default lowered to something like 100 ms?