Duris_I

Hello Dan,

not helpful here probably because of not specific HW to me. I have somewhere my one test between 2 S7-1200 via ISO-TCP but each of different firmw. (4.1 and 3.2). Also TIA version was if I good remember 13 SP1 Upd.8 ????? In that time all was working perfectly via _C intructions??? Really sry, don't remember correctly now...

Hello Ivan - Thanks you for responding.

I went ahead to construct a test program from the sample (see link from 1st entry). Basically I have used the program for the S7-1200 and replicated it to another S7-1200. Some changes like IP address and so, was also needed.

My test program works now - as a simulation. There is still doubt if the original Siemens provided sample would work though. It would be

My next step is to understand the TSAP ID mechanism. 

The TIA internal help does a good job at explaining how the ID is constructed. But my issue is that the test program used the same ID for both send and receive - it still works. My first thought would be that every transaction should have its own ID. Or at least unique per transaction per PLC.

Any thoughts?

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Description of the connection parameters

Address component for an ISO-on-TCP connection. The default value after creating a new ISO-on-TCP connection is E0.01.49.53.4F.6F.6E.54.43.50.2D.31 (S7-1200/1500) or E0.02.49.53.4F.6F.6E.54.43.50.2D.31 (S7-300/400).

You can enter the TSAP-ID with an extension or as an ASCII TSAP.

The TSAPs must be unique on the device!

 It does not seem as though the simulator care about the highlighted caution.

Transport Service Access Points (TSAPs)

Using TSAPs, ISO on TCP protocol and S7 communication allows multiple connections to a
single IP address.TSAPs uniquely identify these communication end point connections to an
IP address.

In the "Address Details" section of the Connection Parameters dialog, you define the TSAPs
to be used. The TSAP of a connection in the CPU is entered in the "Local TSAP" field. The
TSAP assigned for the connection in your partner CPU is entered under the "Partner TSAP"
field

Does the highlighted section mean that each communication transaction has a unique TSAP.

For example, having two PLCs each with send and receive. That makes 4 transactions -> 4 TSAP IDs - right?

Hello Ivan.

It is a pleasure to have the opportunity to chat with you about this topic. Thank you for your contributions.

It is my understanding that the TSAP is like a 2nd address. If a network (think wide area) has two devices with the same IP addresses, these could be isolated from each other by the TSAP.

I studied the topic some more and experimented with different TSAP numbers on a networked program. TIA blocks you for having local and remote partners having the same IP. The 'security' of talking to the right partner with conflicting IPs cannot be tested.

The rules that apply for the port number in TCP, seem to apply for TSAP. The TSAP is important for the passive communication partner, just like (plain) TCP. Having a TSAP for both local and remote partners is redundant, yet most would think to make these the same.

There are naming conventions for the TSAP. This can be in an ASCII or pure number format. This is well documented in TIA Portal help under the heading 'TSAP structure'. It may be worth your while reading this. This is beyond the intended scope of my topic.

Regards.