Ignition & S7-300 Communication

Hi All,

This is my first project with Ignition so please bear with me. I’m setting up a system in which I’ll be communicating a Siemens CPU 315 (CPU 1) with the existing CPU 314 (CPU 2) via MPI. The CPU 315 will be connected to the SCADA PC via Ethernet. I’ll be using the tags from both of the CPU’s. (see below picture for details)

My question is, will Ignition be able to see the tags in “CPU 2” even if it is not directly connected to the PC? If not, should I create a messaging program to transfer tag values to “CPU 1”?

Your help is much appreciated. Thanks a lot!

No, you’ll not see tags from CPU2.
But… if you want to communicate between two Siemens PLC’s over MPI, AFAIK (it was a long time ago), you can only do that (the simplest way) over GLOBAL DATA (right click on MPI network and Define Global Data).
There you must define your sender PLC and receiver PLC. There you also define tags inside receiver PLC, which will get the senders tags.

So, in your case, the PLC1-CPU2 (314) is sender PLC, PLC2-CPU1 (315) is receiver PLC. In the PLC2 you will have all that received tags, which will be seen by Ignition.

Hope it helps…:+1:

I just realized that your picture is from TIA portal. In TIA portal there is no global data anymore…
You must use X_GET and X_PUT blocks, but the idea is the same…


Hello zxcslo,

Thanks for your reply, now everything is clear to me! Just a follow up question (seems that you’re well-experienced with Siemens).

I’ve managed to get to CPU2’s program and it is programmed under Step7. I’ll be using TIA Portal v14 on CPU1. With this, is it possible to establish messaging between those CPU’s?

I’m trying to minimize configuration and program editing at CPU 2 since it’s an existing one and currently running, most of all, it’s not part of my scope anymore. :slight_smile:

Thanks in advance!

Well… you can’t get away without doing some changes also in CPU2 with old Step7…

You see, in order to communicate between two Siemens PLC’s over MPI, both PLC’s must be aware of one another.
That means that in hardware configuration inside both PLC’s there must be both PLC’s.
If I were doing it, I would convert/migrate the old step7 project to TIA (if the old PLC is relatively new; if not then you are…fxxked… :slight_smile: ), transfer the program to the project of your CPU1 (315) and do the hardware config and use X_GET/X_PUT or X_RCV/X_SEND.

If you can’t do that, then you must put your new (315) plc to the old step7 program, change the hardware config of the old CPU (so that both CPU’s are on the same MPI network), and implement inside the old step7 program the X_SEND or X_PUT blocks. Then download the project and hope for the best…:slight_smile:
And the same must be done in TIA portal: putting the old CPU (314) into the HW config, put them on the same MPI network, implement X_GET or X_RCV functions in the new program of CPU1 and download…

All in all… it’s not easy and without risk to break something.

Maybe the easiest way is really to put ethernet CP to the OLD CPU, adding it in the HW config and download the HW config back. Then you can see all the tags in Ignition from CPU2 also…


hmmmm… guess i need to decide on my option…

Well, the third option was indeed the easiest but the problem is there’s no more slot available. I was thinking to purchase those MPI-Ethernet Converter, do you think those are reliable?

If those MPI-Ethernet converters are ‘stand-alone’, (I mean, ‘plug&play’; you plug it into the MPI port and another end into the switch and there is no need for some extra drivers on the PC) then I think you’re OK…

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alright! Guess i’m gonna go with that option.
Thank you very much for your help! It’s greatly appreciated! :slight_smile: :slight_smile: :slight_smile: