Several PLC,s on Ethernet....Profibus DP

Hello!

I have two questions for the ones who knows

Nr 1.
I have set up 2 plc,s in ethernet network using FC5 and FC6. Siemens PLC,s. This is well documented on Siemens webpage, with datasheets and sampleprograms.
It is working properly, I use several connections, and I send several DB,s.

I have also set up a third plc on the same network. Using the FC5 and FC6 I can send send blocks between all the three plc,s.

The plc,s I use are two 315-2 DP with a 343-1 lean card each, and one 315 with a 343-1 card. I set up all the different connections with ISO on TCP connections.

It is working properly, but since I can only find datasheets and examples on FC5 and FC6 with ISO on TCP with two plc,s, my questions goes like this:

Is this a smart way to do it, when you have several plc,s (ISO on TCP)? Does anybody have experience with it?

I don,t want to use this in a plant if there is a negative issue with it that I have not experienced yet...

------------------------

Nr 2.
I want to set up Profibus DP between two plc,s. Each plc is a 315-2 DP and they have a CP 345-2 each.
I will use FC 1 DP-SEND and FC 2 DP-RECV in the program.

I have been told that there is a limitation on 240 Bytes.
Is this a limitation on the FC,s , or is it a limitation on the CP 342-5.????


If it is limited to the FC, then I can just split up the DB which is bigger then 240 Bytes and make it into two DB,s, then call the FC up two times for each DB.

If it is limited to the CP card, then it will not be that easy...

Thank you very much for any answers... appreciate it


regards Andreas

1. ISO on TCP isn't a master/slave protocol. Network collisions are solved at hardware level. You can append 3-rd 300 to your network. It'l work.
Only one recomendation. If you use SCADA with server and clients PC, better to use separate networks for PLCs and clients PCs.
2. 240 bytes is a limit of S7 hardware. If you want to send/receive more data, you must call your FCs with separate DBs in turn.

Thanks alot for answering

Only one thing, when you say :

"240 bytes is a limit of S7 hardware"

What do you mean by S7 Hardware? The FC,s or the CP?

Then you follow up with:

"If you want to send/receive more data, you must call your FCs with separate DBs in turn."

I suppose then that S7 Hardware are the FC,s....So that I can send much more then 240 Bytes on one CP card, as long as I split up the DB,s and use a FC call for each DB ????

regards

I cann't find now link about this. 240 bytes are defined as limit in S7 network protocol. It's maximal packet size for S7-300. This mean you can send to partner just 240 * 1000 bytes - but in turn, in separate FC calls by 240 bytes. How you will fight with data sequence - it's your business.