Data Exchange with multiple STEP 7 Masters

I have several small individual stations, each controlled with a 314C-2DP processor. Right now, a multiproject is used to contain all of the projects. Each PLC is configured as a master in its own project and all of the connections are merged in the project.

The stations are physically connected at the DP ports, and a TP270 sits at one end of the network, communicating with all of the PLCs for simple start, stop, status, ...

We now have to have each of the stations communicate a couple of bytes of data (less than 4) with the station on either side of it. (basically handshaking signals that are currently hardwired)

Station 1 - Station 2, Station 2 to Stations 1 and 3, Station 3 to stations 2 and 4, ....

With the 314C processor, is it possible to configure the masters to exchange a couple of bytes of data like a master and intelligent slave can (MS Mode), or is it only possible with S7-400.

It's an odd configuration because they are training systems. Each station can work by itself, or with the ones on either side. Otherwise I'd make the first stations CPU the master and the others slaves and configure the connection table.

Problem is that the onboard DP ports on the S7-300 CPUs cannot initiate master-to-master data transfers. The ports have "server" functionality but not "client" functionality.
If you open Netpro and try to make a connection between two S7-300 via the DP ports setup as masters, you will find that it is not possible.

Solutions:

Let one PLC be master and the other slaves. Then setup i/o areas in the salves and the master for the datatransfer.

Or, install a Profibus or Ethnernet CP in each PLC.

Or, setup separate DP networks and link them together with DP/Dp couplers.

Or, keep the Profibus ports for DP i/o for each CPU, and let the CPUs exchange data via the MPI ports.

Heres a question from me:
Does Profibus have Global Data like MPI has ?
If yes, then it could be a solution too.
Anyone knows ?

Jesper,


No, Profibus doesn't have global data like MPI that I am aware of.

I don't think the company is going to spring for DP-DP couplers so a single master and multiple slaves is the only option I guess.

Problem with that (with this project) is not all of the stations will be present all of the time. (A customer can buy all of the stations, stations 1,2,and 3, stations 2,3,and 4, ... as long as they have adjacent stations), which means multiple projects, depending on which stations are bought, and a different master. I was hoping to find a way where we could have one project that would cover any configuration, but I don't think that's going to work anymore.