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Entry type: FAQ Entry ID: 39747607, Entry date: 04/04/2016
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SINAMICS G110: How to establish a USS connection.

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  • Associated product(s)
This FAQ applies only to the SINAMICS G110.

How do I establish a USS connection to a G110?


  1. How does the USS protocol function?
    The USS protocol functions according to the master-slave principle. This means that the individual slaves (inverters) are addressed using a request telegram from the master via their parameterizable USS address. The slave then returns a response telegram. A maximum of 31 inverters can be connected to a USS bus, which can communicate with a baud rate of up to 57.6 kbit/s (with S7-200 only 19.200 baud).
  1. How do I proceed when establishing USS communication?

Hardware

  • A shielded three-core cable should be used to establish the connection between the inverter and the master.
  • The USS communication must be connected at the master at interface 0.
  • The cable can then be looped through from inverter to inverter up to the last unit.
  • The inverter is connected at terminals 8 (P+), 9 (N-) and 10 (M/0V).
  • In order to guarantee disturbance-free communication, a terminating resistor must be used at the first and last bus node (bus participant). At the master this is realized between terminals P+ and N-
  • The SINAMICS G110 has a DIP switch at the front to set the terminating resistor.



 

Information regarding SIMATIC S7-200

  • For the S7-200, a PROFIBUS cable with PROFIBUS connector should be used.
  • It should be noted that an extra conductor is provided for the M (0V).
  • The M (0V) should be connected at M (0V) of the S7-200 power supply. It is NOT permissible to use the shield of the BUS cable as M.
  • The terminating resistor at the S7-200 is set using a coding switch at the PROFIBUS connector.#
  • More detailed information is provided in the S7-200 System Manual, Chapter 11 (see link below)
Information regarding USS connection with SIMATIC S7-1200 is provided in S7-1200 Sytem Manual, Chapter 12.4 (see link below)

 

  1. How do I proceed when commissioning and parameterizing?
    In the example, with an S7-200

G110 parameters
(Settings for S7-200)
After the bus has been cabled (connected-up), the USS parameters should be set at the inverter.
The following are set

  • the bus address (P2011 = 0-31),
  • the baud rate (P2010 = 7),
  • the telegram length (P2012 = 2 / P2013 = 127) and
  • the telegram monitoring time (P2014 = depends on the particular plant or system);
these are either parameterized using the optional operator panel or using the STARTER commissioning tool (see link below) that is available free-of-charge. STARTER can run on commercially available PCs and programming devices under Windows NT/2000/XP Professional/Vista/Win7. Instead of the operator panel, a PC adapter with the same dimensions is plugged onto the inverter.

S7-200 programming environment
The S7-200 programming environment is realized using the Step7 Micro/WIN software.
Also refer to: S7 200 System Manual, Chapter 11.

The software should be expanded by a toolbox, which allows the drive to be controlled via the USS protocol. A “new project” should be created in the program for this purpose and the corresponding blocks to initialize and control the USS communication called under the item “Operations -> Libraries -> USS Protocol”.
  • The "USS_INIT" block sets interface 0 of the S7-200 to communication using the USS protocol.
  • Using the "USS_CTRL" block, the control word and the speed setpoint are transferred to the inverter; whereby individual bits of the control word – such as ON/OFF, reversing and fault      acknowledgement – are directly controlled. The speed setpoint transferred is calculated using the reference frequency in the inverter (parameter P2000).
The inverter simultaneously returns the status word and the actual inverter output frequency in the response telegram. This allows possible alarms and faults that have occurred to be identified and it also allows the operating state of the inverter to be diagnosed. By just programming these two blocks, it is now possible to control the inverters on the bus independently of one another and operate them with different frequency setpoints.

Reading and writing the inverter parameters
The programming software provides six additional blocks for these read and write operations – three blocks to read and three blocks to write.

Note
In the parameter list of the SINAMICS G110 there are three different ways of displaying parameters: WORD/U16, DOUBLE/U32 and REAL/float parameters. The user selects the suitable block corresponding to the parameter data type to be changed. When executing a write operation, the inverter operating state must be observed. For instance, some parameters such as e.g. the motor data can only be changed in the commissioning mode; other parameters, e.g. the ramp-up time (acceleration time) can even be changed while the inverter is operational.

Possible applications using SINAMICS G110 and the USS protocol
  • Generating a program blocks in which all of the application-specific parameters and values are described.
    The bus addresses can be incremented using a counter in the S7-200 so that the program block can be quite simply loaded into all G110 bus participants. If a parameter is still to be changed at a later point in time, then it is sufficient to make a single change in the program block – and then the updated value can be written to all of the inverters connected to the bus. A parameter set saved in the operator panel can also be loaded back into the inverter using write operations. This is necessary for instance if a parameter has been accidentally changed and this has to be undone – or a customer-specific parameter set is to be restored
  • Extending the communication possibilities by connecting to PROFIBUS, ASI-Bus, GSM, Ethernet or Internet using additional S7-200 modules.
    This extended communication option of the SIMATIC S7-200 allows the SINAMICS G110 – as the smallest inverter in the SINAMICS family – to be integrated into the Totally Integrated Automation concept of Siemens AG.
  • Storing customer-specific Java Applets on the web server using the IT module with integrated web server.
    These pages can be called using a browser via the Ethernet or Internet. This allows the inverter to be interactively controlled or parameters and be read and written to.
  • Evaluating the inverter operating states within the S7-200.
    When faults occur, the corresponding fault ID can be read-out using a parameter. Passing on the fault using GSM or Internet (e-mail) is conceivable. As a consequence, the user receives a precise fault message for each fault and can then respond specifically and initiate counter measures
Additional information
  • Specification of USS protocol; Entry-ID: 24178253
  • S7 200 System Manual; Entry-ID: 1109582
  • S7 1200 System Manual; Entry-ID: 36932465
  • G110 EMC design guidelines configuration manual; Entry-ID: 60612658
  • Order No. (MLFB) Operator panel: 6SL3255-0AA00-4BA0
  • Order No. (MLFB) PC Adapter: 6SL3255-0AA00-2AA0
  • FAQ: "What are the differences between USS communications on SINAMICS G110 and MICROMASTER 4?”; Entry-ID: 22423773
  • FAQ: "What information is available about using USS Protocol with the MM420?"; Entry-ID: 5734889
  • FAQ: "Recommendations for reliable RS485 communication between S7-200 and MICROMASTER 4"; Entry-ID: 12462284
  • Download: SINAMICS MICROMASTER STARTER; Entry-ID: 26233208
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https://www.siemens.com/cybersecurity#Ouraspiration.