Swapping the PLC

I have a case where we have a client swapping out their OMRON PLC for a Siemens PLC.

Is there any easy way in Ignition to find and change all the tags/tag bindings or is it going to be as labor intensive as I think and have to manually go through everything?

Recreating the device connection is fine, but the OPC paths will be different.

I would export the tags, change the OPC path, then re-import them.

Keep in mind Siemens PLC doesn't let you browse the tags automatically like other drivers. For the OPC paths you'll need to write the DB no. and offsets for all your tags, you can't use tag names.

If possible take a backup of your current tags and do some find and replace to put in this new information or use a script to do it for you.

e.g. ns=1;s=[Device Name]DB100,I6.0 for an integer in DB100

Omron and Siemens tag addressing is totally different, so, yes.

You definitively can use tag names if you use symbolic addressing with optimized block access.

Not an option with our Siemens driver.

You would need to use the built-in OPC UA server that S7-1200 and S7-1500 have, and make an OPC connection instead.


That's right indeed. But is there any reason why you wouldn't? I find it makes things a lot easier and more flexible

Because Siemens doesn't document the S7 protocol at all, much less the newer "S7 Plus" extensions that allow for this.

If I remember right, if you use the OPC UA version and read Siemens User Defined Data Types they come as a JSON struct, I don't know if this is still the case as we've used the Siemens driver for a while. We often used and still do use a lot of these structures but don't use all of the values in them for the HMI.

We tend to find it a lot easier to define an Ignition UDT, with a DB no. and start offset as parameters. Then can initialise all of these for our systems.

Also, I think for models of PLC you're limited to a maximum of 1000 items you can monitor using the OPC UA. Not usually a big deal, but if we have a lot of alarming or other statuses sometimes we can get a bit close for comfort.

The 1000 items subscription is not a hard limit : it can be changed in the hardware configuration if needed.
I guess the more items available, the more impactful it will be on the cycle time.
That might be why Siemens is going bi-cpu in their new PLCs, one for the logic and one for the comm (I heard about it but did not see it).
Regarding UDT, we also do UDTs but with symbolic addressing as we tend to change datablocs a lot, adding or moving items in it. Symbolic adressing works wonder for that matter.