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Entry type: FAQ Entry ID: 19364531, Entry date: 04/28/2010

How do you interface and configure a 'SIMODRIVE sensor isochron' (synchronous PROFIBUS DP encoder) on Technology CPU?

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Proceed as follows to interface a 'SIMODRIVE sensor isochron' synchronous PROFIBUS DP encoder (order no.: 6FX2001-5xPxx) to a Technology CPU.

  • Configure the synchronous PROFIBUS DP encoder
  • Parameterize the synchronous PROFIBUS DP encoder
  • Upload the hardware configuration into the CPU
  • Configure the technology object of the synchronous PROFIBUS DP encoder
  • Create the Technology DBs
  • Insert the FB MC_ExternalEncoder

1. Configure the synchronous PROFIBUS DP encoder

  • Insert the encoder into your project from the hardware catalog. It is located under "PROFIBUS_DP >SIMODRIVE" (Fig. 1).
    • First use drag-and-drop to incorporate the encoder into the PROFIBUS master system. 
    • Now insert Telegram 81 into Slot 1 of the encoder station.

Fig. 01: Encoder selection in the hardware catalog 

 2. Parameterize the synchronous PROFIBUS DP encoder

  • Right-click on the slave (Fig. 01: top half) and go to "Object Properties". In the "Parameter Assignment" tab you set the values that are located in the line of the encoder you implemented under "SIMOTION HW Config" in Entry ID 18769911.

Fig. 02: Example of parameter assignment from the "List of usable encoders" (Entry ID: 18769911)

Fig. 03: Assigning DP slave parameters

  • Then, in the "Isochrone Mode" tab, you enable the option "Synchronize DP slave to constant DP bus cycle time" and set the relevant values for the times for read-in and output of the process values. Using the default values of the encoder you can set the following Ti/To values, for example:

    Ti min   : = 0.125 ms
    To min  : = 0.375 ms     

    More information on the topic of isochrone mode and Ti/To is available in the manual "SIMATIC Isochrone Mode", section 2.8.3 in Entry ID: 15218045  and in the manual "SIMODRIVE sensor absolute value encoder PROFIBUS DP" (User's Guide), Chapter 10, Edition 03/04, Order no. 6SN 1197-0AB10 - 0YP3.

Fig. 04: Synchronizing the DP slave

  • Confirm your entries with "OK". 
    If there are several nodes active on the synchronous bus, you might get error messages like"... time To is too small". Increase the time accordingly and confirm your entries with "OK". 
  • Upload the hardware configuration into the CPU with "PLC > Upload to Module".

4.  Configure the absolute encoder Technology object

  • In the SIMATIC Manager you switch to the S7 project and select the "Technology" folder.
  • Start the S7T Config (configure Technology).  
  • Select the menu command Add > Technological Object > External Encoder.
  • Assign a name for this encoder and confirm with "OK".
  • Configure the encoder:
    • Click in an input field and do not move the cursor and the SIMOTION name of the parameter is displayed in the tooltip. This name is located in the line of the encoder you implemented under "SIMOTION Axis" in Entry ID 18769911 (see also Fig. 02).
    • You can accept the default values for "Mechanics" and "Default value".

Fig. 05: Configuring the external encoder
  • Complete encoder configuration with "Finish".
  • "Save and compile" the configuration.
  • Close the Hardware Configuration.

5. Create the Technology DBs

  • Start the Technology Objects Manager (TOM). The DBs that have not yet been created are displayed. Click the "Create" button to transfer these DBs into the block folder and then close the window. 
  • The offline block folder now contains the blocks created with TOM.

6. Insert the FB MC_ExternalEncoder

  • Insert the FB432 "MC_ExternalEncoder" into the block folder from the "S7 Tech" library.
  • In OB1, call FB 432 and generate an associated instance data block.
  • Enter the relevant necessary parameters "Axis" (number of the technology DB for the external encoder) and "Mode" (operating mode). Save OB1. 

    Fig. 06: Calling FB 432 in OB1
  • Transfer all the blocks into the CPU.
  • After successful transfer into the target system you can check the function of the encoder in a variable table.
    The actual value of the encoder is returned under "Actual Position" in the Technology DB.   

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