Data transfer to other PLCs with Siemens

Hi there. I will need to receive a large DB worth of data in my siemens 319 CPU from a different processor. I know that between siemens processors, a UDP connection can be established, and data can be sent and received with AG_Send and AG_Receive. Does this also work for non-siemens processors?

A profibus node won't work because the data to be sent will be about 14000 bytes.

I imagine I'll have to receive several packets of data instead of all at one time because of the huge data amount.

AG_Receive is for up to just 240 bytes. What amount can AG_LReceive handle?

I'd appreciate any input!

-dmbartender

If you are planning to use the onboard PN port in the 319, then you cannot use AG_SEND/AG_RECV. AG_SEND/AG_RECV requires a CP343-1.
I think that AG_LSEND/AG_LRECV can only be used with CPs in an S7-400.

With the onboard PN port you can use the "open communication blocks". TSEND, TRECV, TCON etc from the standard library.
For an S7-319, the max data lengths are as follows:
TCP and ISO-on-TCP: 8192 Bytes
UDP: 1472 Bytes

You can also use S7 connections with PUT/GET blocks, however these are specific to Siemens PLCs etc. I have not heard that there are other PLCs that can connect with an S7 connection. Maybe a VIPA can.

If you can get the communication partner at the other end to talk with these blocks is another matter.
What kind of PLC is it then ?

I will have a CP 343 as well, so that's no problem. Unfortunately I don't know yet which type of plc the other will be. That has yet to be determined. It must be possible though, like coupling S7 and CLX processors together.

So the maximum is 8192 bytes with TCP or ISO on TCP? I wonder why one can transfer larger packets with the TCP protocol compared to the UDP.

Using the AG_LSend and AS_LReceive would be the way to go though, considering the large packet, right?

With recent versions of CP343-1, and AG_SEND/AG_RECV blocks of version 4.2/4.7 or higher, you can transfer up to 8192 Bytes.
http://support.automation.siemens.com/WW/view/en/16533272

However, you should keep in mind that all the data has to pass through the slow backplane bus of the S7-300 (MPI at 187.5kbps).
For a lot of data I have heard examples of transfers taking seconds, not milliseconds, to finish.

dmbartender said:

It must be possible though, like coupling S7 and CLX processors together.

Click to expand...

Yes, I have heard about people that have accomplished this. However, it is not trivial, and you cannot take for granted that it will be possible with other PLCs.
"Ethernet" is not a standard in the PLC world.

HI Jesper,

Thanks for all the quick answers! For what I want it's not so critical if the transfer takes a couple seconds. I'll probably break it up into 3 different TCP or ISO on TCP connections, each with about 4500 bytes.

What is the general difference by the way, between a normal TCP and ISO on TCP connections for Siemens?

dmbartender said:

What is the general difference by the way, between a normal TCP and ISO on TCP connections for Siemens?

Click to expand...

That is a good question. I do not think that there is a difference performance-wise. The difference is how the connection is specified.
With TCP you need to specify IP and ports.
With ISO-on-TCP you have to specify IP and "TSAP" which is a unique 16-byte identifier.
With ISO you have to specify MAC and TSAP.

edit: Actually, I think that ISO is faster than TCP because it uses a lower-level access via the MAC addresses. If ISO-on-TCP is like ISO or like TCP in this respect I do not know.

There is a "wizard" for estimating data transfer times:
http://support.automation.siemens.com/WW/view/en/22180793

Not all combinations are possible with this wizard.
Why a 319 is not possible I do not know, but with a 317+CP343-1 and ISO-on-TCP and 8192 bytes, transmission time is approximately 1 second.

Thanks for the tip Jesper! I'm excited to try out a few different configuration methods, and see just how long it takes to transfer so much data.


If anyone here has used such methods to transfer large blocks of data, I'd be interested to hear your results.

Cheers