Informations

Communication process

Prinzip
Information on communication process: Ablauf

As illustrated below, the communication driver processes 4 lists in this order. Consequently, the priority for transferring function keys and set values is very high.

For obtaining shorter refresh times, the following should be considered:

  1. Always use the station process connections for the fault and functional messages. Individual process connections may only be used for certain fault and/or functional messages (VISU class only).
  2. When creating a project, make sure you use subsequent registers in the order which is used for inserting the variables into the process image.
  3. If possible, do not use any variables with permanent updating, you should only use them if absolutely necessary (VISU class only).
  4. When you are manipulating bits in ProVicom/Exicom, these may only be used as set values. A simultaneous manipulation of device and PLC does not work (VISU class only).
  5. Adjust the measuring cycle to suitable values. When all variables are adjusted to a basic setting of 200 msec, the driver is cannot carry out a time-relevant query (VISU class only).
  6. The PLC and/or the PLS also have an important role. The data query must be answered as soon as possible. For this reason, please do not exceed the following values:
    A ) Communication drivers in the operating system (e.g. S5-AS511, S7-MPI, Modicon Modbus, TI-505...)
    In this case, the refresh time directly depends on the PLC cycle.
    The recommended cycle time amounts to 50 - 70ms.
    B ) Communication driver as functional component with one polling per data exchange
    (e.g. S7 400 CP-441)
    max. cycle /polling time amounts to 50 - 70ms.
    C ) Communication driver as functional component with one polling per data exchange
    (e.g. S7 300 CP-340 / CP-341, Interbus-S, Profibus)
    The polling time must be shorter than 50ms.