Siemens CPU 319-3+CP343-1 optimize performance by C-Bus?

[Kasperv79]

Hi guys.

I been searching and reading a lot about CP341 and other external communications cards on S7-300 series CPU. but I'm still confused.


So..

We do have a production runing Ifix SCADA with a keepware OPC server. Several S7-300 series hooked on the ethernet by vendors.

The problem is that when using the external CP for communication to SCADA the porformance is very poor compared when using the internal CP card.


We cannot just change to use the internal CP card as it is used for some servo drives and the external card is to slow for this.


Is there any way to speed up the external CP card to perform as the internal?
the external CP is usug both C/K-Bus and P-Bus, is there any effect by increasing the C/K-bus from 185.kb/sec to 12MB/sec? or is the MPI C/K-Bus a seperate bus.?


Kasper

 

[mk42]

One of the downsides of the S7-300 family compared to the S7-400 or the newer S7-1500 is a slow backplane and decreased communications capability. As far as I know, the backplane speeds cannot be changed.

However, you may be able to speed things up some if your PLC supports "Prioritized OCM communication". This changed hos communications are prioritized within the CPU. See below:

https://support.industry.siemens.com/cs/us/en/view/49749632

 

[Lare]

Is you servo drives on different ip range on internal cp
TCP can be client and slave same time

 

[JesperMP]

Hej Kasper

Yes, the SCADA traffic when connected to the CP343-1 will pass over the MPI based backplane which is pitifully slow.

Your SCADA can probably connect to the same Ethernet port as your servo drives are connected to without any problem.
The performance of the intergrated PN port is plenty good enough for both.
Your servo drives will not feel any difference. The Profinet traffic is prioritised over regular TCP/IP, and the Profinet update time will not change even the slightest.

If IP addresses are different, then you can place a router between the 319 and your SCADA.

 

[Bratt]

Hej Kasper

If IP addresses are different, then you can place a router between the 319 and your SCADA.

A common way to do this at least among my customers is to use a Siemens S602.

 

[Kasperv79]

Thanks.
So changing MPI speed will not make any difference.?

The two network cards must be seperated (one for CORP and one for machine components)

 

[JesperMP]

So changing MPI speed will not make any difference.?

No it will not make any difference. The MPI speed that you can change is for the MPI/DP port. The K-bus speed is not influenced by this on a 319 CPU.

The two network cards must be seperated (one for CORP and one for machine components)

Like I and Bratt suggested, you can separate machine and customer LANs with a Router.
If IP adresses have to be adapted, a 1-to-1 NAT Router can fix that. It is normally not necessary. A router connects different networks together so your SCADA can access the 319 PLC even if it is in a different network with a different setup of IP adresses.
The S602 Bratt linked to is a Router with extra security and integrated 1-to-1 NAT Router.

 

[mk42]

Siemens also has a newer module called the S615 that I think is a little easier to configure and is a little cheaper than the S602. It's definitely smaller, as well.

 

[Kasperv79]

Thanks for all the replys.
I agree that a router could solve the problem.
It's jut that we are very restricted to follow some local factory requirements. that means that machine and MES must be at separate adapters.

 

[JesperMP]

Talk to them about a 1-to-1 NAT router. This really separates the two networks as far as it is possible. The 1-to-1 NAT router can be considered a "separate adapter".

If they cannot accept any such solution, then they must on the other hand accept that the performance on the MES network is very low.
Present it to them that it is their own choice what they prefer.