S7-300 Profibus Comms

Hi,

How can I get two or more S7-300 PLCS to communicate to each other.
Im using Step 7 5.4 and the plcs are all connected using profibus.

Is there a remote IO block i need to add in Hardware config and then point this to a db area in each plc.....i do not know?

Any ideas appreciated....thanks!

Coops

There are a couple of answers here depending on how you want to do this. Are you wanting to have a master - slave configuration or just send a bit of data from one PLC to another?

Module D6 on this page deals with master slave configuration for two 315-2DP's.

I am sure that if you search this site you will find some examples of communications using the various SFC's available.

Paul

Personally if I'm passing info between PLC's via profibus, I would normally use DP Couplers, much easier.

Peter, that's cheating!

Plus Coops has said "[they] are all connected using profibus." So is one a master already and all the others slaves? Would you propose creating multiple networks and then changing the PLC configurations just to use DP couplers between multiple masters?

I think on the present evidence, Paul's suggestion is better in this case. (Although the DP Coupler is an excellent piece of equipment - small, tidy, does just what it says, and so easy to use in the right application.)

Ken

We need more info.

Are we talking about onboard DP ports in CPUs like 314C-2DP and 315-2DP. Or are we talking about CPUs with CP343-5 Profibus modules.
Are there other things connected on the Profibus network(s), such as slaves or OPs ?
How much data and how often ?

I have 4 Plcs on a profibus network and I just want them to be able to pass data to each other via DB's. Would all these plc programs all have to be part of the same step7 project or can they be in different ones?

Hello Coops;
You can setup a FDL connection over Profibus-DP (in Netpro) for each DP-master, which will allow some form of peer-to-peer connection; then use AG_Send and AG-Recieve functions (see below) to transfer a DB (up to 240 bytes long) between 2 partners in your program. You can also send multiple DBs (one at a tiome) between 2 partners. You identify the sender and reciever PLCs through their ID generated by Netpro.
For more details, look on the online help for AG_SEND and AG_RECV (Profibus)

From the S7_communications manual:
For the purpose of processing the communication via links, two loadable FC blocks are available:
Block Description
FC 5 AG_SEND This sends data blocks via a configured link to a
communication partner
FC 6 AG_RECV This receives data blocks via a configured link from a communication partner
You will find the loadable blocks in SIMATIC Manager, if you have installed the appropriate NCM option package, as follows:
Open file -> Library -> SIMATIC_NET_CP -> CP_300 or CP_400 ->
blocks.
Size of Useful Data: The maximum size of useful data that can be transferred is limited to 240 bytes for all subnets.
Data Consistency: In SIMATIC S7, data up to a maximum length of 240 bytes can be transferred consistently.
Link Resources: For each link, a link resource is required on the CP. STEP 7 checks during configuration whether sufficient link resources are available.
Interrupt Response:
The communication FCs AG_SEND and AG_RECV cannot be interrupted
by OBs of a higher priority and can in certain cases therefore cause the interrupt response time to be extended.
Addressing: The communication partner is addressed via the local link end point (local ID). The local ID is generated by STEP 7 when the link is configured. The communication partner can also be located within another S7 project. The local ID is only loaded when the communication FC is initially called and remains valid until the next complete restart.

Hope this helps,
Daniel Chartier

All the plc's on the network will be masters. Will this cause a problem?

I still say DP Couplers are easier it maybe cheating :nodi: but its a whole lot easier when you have nothing to program.

What else is the network used for, I've never mixed I/O on a network shared by more than one controller.

GUESS HERE: shared HMI?

Peter - How many DP couplers would be required for connecting 4 CPU's together ?

JesperMP said:

We need more info.

Are we talking about onboard DP ports in CPUs like 314C-2DP and 315-2DP. Or are we talking about CPUs with CP343-5 Profibus modules.
Are there other things connected on the Profibus network(s), such as slaves or OPs ?
How much data and how often ?

Click to expand...

Question repeated.

SimonGoldsworthy said:

Peter - How many DP couplers would be required for connecting 4 CPU's together ?

Click to expand...

erm.... 4 well do they all need to talk to each other?

recently I've worked almost exclusively with conveyors, therefore area a would connect to b and b to c but c would never want to talk to a.

If its some sort of batching system, then fair enough there maybe required more links.


erm.... 4 (for my sort of systems 3, can't even get that right )

There are two 315-2DPs and two 314's all using dp ports not CP comms cards. There maybe OP's and if there is then i can't use the systems the as the easier method of master and 3 slaves. Not sure if AG_Send will work without a CP comms card. Any ideas

For communication between PLC's I always use the MPI ports. The DP port is only used for decentral I/O and HMI. When I need to communicate by means of Profibus, I use a seperate CP. This happend only once, normaly we use TCP/IP to communicate with other party's.

Cheers Garcia, but i've got what i got at the moment; and that is 4plc's with DP ports. .

I've tested the system as a master / slave system and it works very well indeed. But i have yet to find out from the customer if anything is going to sit on the Slave PLC's profibus...if there is then i need to do a re-think