PROFIBUS communications


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We have a flow transmitter (Proline PROMAG 53 W from Endress + Hauser), a Soft-PLC (WinAC from Siemens) and a PROFIBUS DP-network. As communication card in our PC (PROFIBUS) we use a DP4513 from Siemens. PROBLEM: Each time we use the flow in our program (SIMATIC S7) the PLC goes
into STOP-mode. When we do not use the flow in our program (flow transmitter NOT disconnected) there is no problem. In the variable table of SIMATIC S7 we CAN read the flow.
Could you tell me what the problem is (Soft-PLC or flow transmitter) and how I have to solve this problem

Hakan Ozevin

You have to look at the diagnostic data of the CPU. (In STEP 7, Select the CPU and use menu command PLC>Diagnose Hardware).
The reason of the STOP condition is written there. According to the reason, you may think to program some OB's.

Rolf Birkhofer

A possible problem could be, that the flow value is transported with a status byte via the Profibus. That is 5 Byte for each data_exchange cycle. From my experience,early versions of S7-PLCs could not transport 5 Byte consistently
from the DP-Master memory to the CPU memory (because there is no 5 Byte data type).
If this is still the case, the solution is to fetch the flow value via the SFC14. This function decodes the 5 Byte value and offers you a dword. It has tob called in your PLC user program.
Hope that helps.