Multiple em 277

Hello Rafael;

You could easily connect a large number of EM 277 Profibus slaves to a DP master.

Unfortunately, the S7-200 CPUs cannot act as Profibus masters, so this option is void.

You could look into other Siemens families of PLCs (S7-300, ET 200S, S7-1200) to setup a DP master, but you would need extra hardware and programming software.

One option would be to devise a PPI network (one master, 2 slaves, connected with Profibus cables for example) with your existing PLCs. You would have to look up the NETR/NETW instructions of MicroWin in the online help, or in the S7-200 system manual.

This linkshould also help:

How is data exchanged between two SIMATIC S7-200 in PPI mode

https://support.automation.siemens.com/WW/llisapi.dll?func=cslib.csinfo&objId=370000&ehbid=370000&hlnav=yes&skm=1&content=adsearch%2Fadsearch%2Easpx&cssearchengine=new&lang=en&siteid=cseus&aktprim=0&objaction=csopen&extranet=standard&viewreg=WW

Hope this helps,

Daniel Chartier

Hi Daniel,

Thank you for your reply.

I have received more information from the customer and it changes the story a little bit.I will try to explain it:

The whole system has 2 subsystems (A/B). Both subsystems communicate via profibus (subsystem A is the masterand subsystem B is the slave). The customer is upgrading subsystem B but subsystem A cannot be modified.

Original (old) set up:

-subsystem A: profibus master (unknown controller)

-subsystem B: profibus slave (S7-200 with EM277)

On the new set up:

-subsystem A: profibus master (unknown controller) (It cannot be modified)

-subsystem B: 2 profibus slaves (Allen Bradley)

Requirement:

- Create an "interface" system that will allow new subsystem B to communicate to subsystem A knowing that subsystem A cannot be modified.

-Only 1 of the profibus slaves on the new subsystem B need to communicate with subsystem A at a time

Proposal for the "interface" system

- Keep the S7-200 with the EM277 to communicate with subsystem A

-Add another EM277 to the S7-200

-Add a S7-1200 (or it could be a S7-300) as a profibus master to communicate with the slaves on the new subsystem B and the EM277 added to the S7-200.

I have attached picture in hope it will make the idea clear.

Knowing the constraints ofsubsystem A and the new subsytem B, can the "interface" proposal arrangement work? Is the S7-200 capable of having 2 EM277 connected to it?

Thanks.

Thank you for the replies.

mops04, the problem is that system A cannot be modified (the profibus master cannot evenbe reconfigured for new/different slaves). The existing system B already has a S7-200 so we are trying to keep this S7-200 to do the data exchange between the system A and the new system B so that way the profibus master in system A does not need to change or be reconfigured.

Rafaelsb

Thank you for the replies.

mops04, the problem is that system A cannot be modified (the profibus master cannot evenbe reconfigured for new/different slaves). The existing system B already has a S7-200 so we are trying to keep this S7-200 to do the data exchange between the system A and the new system B so that way the profibus master in system A does not need to change or be reconfigured.