S7 200 PROFIBUS COMMUNICATION

Hi guys,

I have a challenge here which I hope you can advise me on;

I have an S7 200 slave CPU which is connected to S7 300 through EM277 Profibus DP Module. I have the DP module in my S7 300 hardware with input and output addresses. Sending or receiving data on the S7 300 side won't be any challenge. However, I need to send some information from the S7 200 to the S7 300 (master CPU) and I don't know how to do this. Please advise me.

Thanks in advance!

Hello Kiiza;

The trick here is to coordinate output addresses from the S7-300 Profibus master with corresponding input addresses on the S7-200 slave: this will be used to send data from the S7-300 to the S7-200. And then creating the same type of exchange (input addresses to the S7-300 master to output addresses of the S7-200 slave) to send data from the S7-200 to the S7-300.

What is tricky is that addressing does not use the same format in both PLC families. The s7-300 uses IW and QW, the S7-200 uses VW registers. So they must be coordinated in the Profibus configuration.

An example of this creation of "exchange zones" between an S7-300 Profibus master and a S7-200 slave can be found in the following FAQ:

How can you communicate data between the S7-200 and the S7-300 via PROFIBUS DP?

In your project follow the same steps as shown there, and adjust the addressing to conform to your requirements on both PLCs.

Hope this helps,

Daniel Chartier

Thanks a lot Daniel,

It did help me.

Could you please advise me about my user program on the S7 200 PLC. My I/O offset is 0 and I have 16Word input/16Word output. some of the data is analog real and I have some digitals. My interest is to send from S7 200 slave to S7 300 master, just one direction traffic. I saw an example in the pdf attached but my challenge is how to attach the data I have on the S7 200 to the data exchange.

Thanks in advance.

Hello Kiiza;

First point: the S7-200 is a slave, and cannot initiate sending data to the Profibus master. The configuration is completely defined in the master, and is seen from the master's point of view: data IN (IB 10, IB11 is the Receive area as seen in the master shown in point 7 of the previous post ) as defined is data that is requested from the slave; data OUT ((QB10, QB11... the Send area of the master in the same description) will be sent to the Profibus slave, your EM 277.

Note that the FAQ uses German mnemonics, so EB10 corresponds in English addressing to IB10, AW10 to QW10.

So if you wish to have the master receive data in the two bytes of its receive area (IB10/11 in the earlier FAQ), in your S7-200 program you must transfer the data of the S7-200 to be sent to the Profibus master in VB102/103.

I suggest you build a table of the data to be transmitted to the master, determine the size (in bytes) of the data to be transmitted, reserve a Send area for the S7-200 of the same size, and start moving data of the S7-200 to the revered VBxx.

Hope this helps,

Daniel Chartier

Thanks a lot Daniel.

i managed to establish communication between the two CPUs. However, my challenge is still how to write the data on the S7 200 into the Variable memory. Do I have to write it there as words? I wrote my analogs there as real and boolean data types and I couldn't receive anything on the S7 300. Or do I need a cyclic exchange in which I make use of SFC 14 and SFC15?

Hello,

if I good understand, you've managed connection, and reserved some V memory area on your S7-200, f.ex.  for Input - V4000, for Output - V5000. Then you can write your data as you wish, but with correct same TYPE definition on S7-300 buffer side.

1. I got on S7-200 MW40 - is number of some steps to give S7-300.

How to give S7-300 this?

VW5000:=MW40.    I know this is SCL format, but is simple to understand what to do. You give to DP I/O buffer at some offset your variable value.

2. I need read from S7-300 f.ex. HW digital output what give me S7-300 via my Input area - V4000.

On that V4000.1 I will got it everytime, when S7-300 via DP refresh it.

Only you must carefully write your requirements of preparing areas of TYPE - (Bit/BYTE/WORD/DWORD) and this schema must be same on S7-300 and S7-200!

I managed to get the communication perfect. And I managed to get the data on to the S7 300. But I still have a question about the Special memory bytes that relate to the profibus communication on S7 200 CPU.

I saw an example that quotes the following special memory bytes for CPU 224 which is the CPU am Using.

SMW220  DP Module Error Status

SMB224     DP Status

SMB225     Master Address

SMW226    V Memory offset for outputs

SMB228     Number of bytes of output data

SMB229     Number of bytes of input data

I monitored these special memory areas after getting my S7 200 in data exchange mode. However all of them had values of 0(zero). My S7 200 is CPU 224 REL 02.01 part number  214-1BD23-0XB0. Could you please advise me on which special memory areas to use for these paarameters.

Thanks in advance.

Hello,

ok pls check that adresses depends to exactly S7-200 DP module slot, because they depends on DP module Slot number. We don't know your exactly S7-200 HW profile, so check this for first, look at SMBxx ranges in S7-200 documentation. If I'm right, probably you're looking to not correct area.