PROFIBUS DP/PA with Siemens S5/IM308-C/IM157


Thread Starter

Mark Hutton

Hi folks,

I'm here on site desperately trying to get my network up and running.

I have had a modicum of success in that I can now see one of the transmitters in the PLC data table (can't make sense of the data yet though). The trouble is it isn't the transmitter I think it is according to the address I believe that I am reading.

COM Profibus configures what it calls 'slots' on the PA side of the IM157, I believe that the slot coresponds to the Profibus address. What is appearing to write to slot 4 should be the device with address 4 (I believe), but the device that I am reliably informed is addressed as 4 is unpowered.

Any suggestions?

Also has any one any experience of using E&H Commuwin II with this kit? I cannot seem to get the server to detect any stations.

Thanks in advance for any help.

Mark Hutton
Software Engineer
mailto:[email protected]
My YAC: +44 (0)7092 032237 (direct access, voice mail and fax
Hello again,

I am going to answer my own post, or part of it anyway for those of you who are interested.

It was a configuration problem.

In COM Profibus when the PA slaves are configured, you are given a grid in which to enter the ID and host mapping information, etc.

Each row in this grid corresponds to a 'slot', the slots are numbered from 0 upwards. There is no information supplied as to how all this
maps to the PA slave address. The assumption made when this was configured, that slot 1 = PA slave 1, etc. In actual fact, slot 0 = slave 3, slot 1=slave 4 etc. It is not quite as simple as that, as some slaves take up more than one slot, they still only have one address, but you can get the picture.

I would still like to hear from any one who has experienced using E&H Commuwin II with a Siemens DP/PA network.

Mark Hutton
Software Engineer
mailto:[email protected]
My YAC: +44 (0)7092 032237 (direct access, voice mail and fax
Yes, Profibus PA & Simatic-S5 seems to be NO friends of each other!
I recently did a project on this subject and I found out that there are quite some problems with this combination. PA & S7 works just fine, no worries, but PA & S5........
The following problems I found:

* If PA-instruments are not in the GSD-file of the IM157, you manually have to put the parameters of the PA-GSD-file into the IM157 GSD-file.
* Yes, the first PA-slavenumber is 3 and starts in slot 0 (ComProfibus).
* Always use the complete parametrising between "BEGIN" & "END" when using complex slaves, so something like:
0 Krohne IFC 090 BEGIN
1 Flow PW128
2 Krohne IFC 090 END
* Never parametrise Outputs in the O-address field in ComProfibus! It won't work.
* Always use FB192 to read Inputs and write Outputs and never write your own statements to read inputs and write outputs. FB192 reads/writes complete blocks.
* Normally measured values are 5 byte long. 4 bytes for the value and 1 for a statusbyte.
* ComProfibus can use a so called "follow-up-byte" to get 6 bytes in stead of 5, but I never got this working. So, your I/O-bytes will
be straight behind each other in your Datablock (if you let FB192 put the I/O bytes into Datablocks). This is not so nice because sometimes your measured value starts at the right byte in a data word.....
* Measured values and setpoints are always in floatingpoint IEEE format. S5 works with it's own format, so you have to convert your floatingpoints
from and to IEEE. (There is a standard functionblock which can do that).
* The 5th byte is the statusbyte. With measured values 80h means: value OK. When sending a setpoint to a PA device you have to send
a 80h in the 5th byte, otherwise the PA device will throw your setpoint in the bin......
* The IM308c is a kind of slow comparing to a modern IM157. So sometimes your bus won't work on >187Kb/s. The best way to make it work is to set
your bus profile from "PROFIBUS-DP" to "DP/FMS" (in Bus Parameters of ComProfibus). With this, the starting up of the PLC is much faster also.
The Target Rotation Timing is a bit longer then with the profile set to default "PROFIBUS-DP" which can be a problem in practice.

If you consider all these things, Profibus PA & Simatic-S5 will be friend for life.......