I'm currently in the process of translating an in-house developed SCADA solution to Ignition. In all previous projects using Allen-Bradley PLC's I've just used Ignition's built-in Logix Driver to connect to the PLC without any discernable issues. For this project our group has been told by a Rockwell rep that the PLC in question has a limit to the number of tags that can be referenced using this connection method and they recommended using FTLinx Gateway instead. I've never heard of this limitation before. Is there any validity to this?
Yes, especially if you'll be accessing AOIs and pre-defined types, or your application is otherwise not optimally structured for efficient access by the drivers.
It's not a hard limit on the number of tags, it's more that you'll max out the comms capability of the PLC sooner than later in these circumstances.
FTLinx has some proprietary access methods that perform better, including some that even Phil's driver doesn't support. (his driver does have reverse engineered support for reading AOIs efficiently as long as they contain no members that aren't externally accessible)
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It is also possible that the Rockwell rep is confused, and is citing the limits in the PLC's OPC UA support.
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I'd bet this is likely the case and as soon OPC-UA is brought up, Rockwell thinks of the only way to do OPC-UA with a ControlLogix is in v36+ and that's very limited. You always have to keep in mind with these vendors that they know their products well, but usually know almost nothing about anything else.
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