Siemens Industry Online Support
Siemens AG
Entry type: FAQ Entry ID: 18845471, Entry date: 04/26/2004

The Operator Panel sporadically displays the error message: "$044 Transfer error ... "

  • Entry
  • Associated product(s)

What is the meaning of the error message "$044 Transfer error ... " that is displayed sporadically on the OP?

During communication with the controller the error message "$044 Transfer error ... " that is displayed sporadically on the OP.
This message is output when the connection between the OP and the controller is defective. Possible causes can be faults in the transfer segment (bus faults on MPI/ PROFIBUS) or also wrongly set interface parameters on the Operator Panel or on the controller.

Please check the following points to clear this fault:

  • Connection of the OP to the controller
    To ensure correct connection of the OP to the controller we recommend configuring using the ProTool option "STEP 7 integrated". This means that your ProTool configuration is a component of the STEP 7 project. If you connect the OP correctly to the available MPI or PROFIBUS subnetwork of the CPU (ProTool: Entry "Controller" see Fig. 1), the OP is inserted as bus node and taken into account in the calculation of the bus times in NetPro (see Fig. 2).

Fig. 1: Connection in ProTool

Fig. 2: Bus nodes in NetPro

If it is not possible to integrate the OP project in STEP 7, you can change the bus times as "user defined" (see Properties of PROFIBUS). In this case you increase the target rotation time (TRT) so that the CPU can communicate with the OP.

  • Observation of PROFIBUS installation guidelines
    Detailed information on the installation guidelines for PROFIBUS and MPI subnetworks is available in the manual "SIMATIC S7-400 and M7-400 Programmable Controllers Hardware and Installation", Chapter 5 Networking in Entry ID: 1117849.
  • Observation of EMC guidelines
    Please strictly observe the EMC (electromagnetic compatibility) guidelines when installing.
  • Number of OP connections of the CPU
    Check the number of connection resources of your CPU. Refer here to the technical data of the CPU.
  • Defective OP interface
    In rare cases it might also happen that the interface on the OP is defective. In this event replace the OP.

OP7, OP17, OP27, OP37, TP27, TP37, Bus faults

Security information
In order to protect technical infrastructures, systems, machines and networks against cyber threats, it is necessary to implement – and continuously maintain – a holistic, state-of-the-art IT security concept. Siemens’ products and solutions constitute one element of such a concept. For more information about cyber security, please visit