Hot Topic: Interfacing RTDS Simulator to External Equipment Using Aurora Protocol

Hot Topic: Interfacing RTDS Simulator to External Equipment Using Aurora Protocol

The Aurora protocol is a lightweight serial protocol developed by Xilinx that is suitable for high speed point-to-point communication links. Support for the Aurora protocol exist for PB5 and NovaCor based RTDS Simulators and is available within both the main timestep and small timestep simulation environments.  Aurora specifications for the PB5 and NovaCor hardwares are similar but slight differences do exist.  The overview provided here focuses on the NovaCor implementation.

The RTDS Simulator’s Aurora protocol implementation allows the bi-directional exchange of 32-bit integers or floating point numbers between the simulator and another Aurora protocol compatible device.  Signals are exchanged via a fiber optic cable. 

The ability to output or read-in Aurora formatted packets must be licenced for each PB5 card or NovaCor chassis.  Each license allows for interconnections over 4 different fiber optic cables.  Each fiber optic connection supports the output of 1-64 numbers as well as the input of 1-64 numbers.

In order to read or write Aurora data to/from a fiber optic cable, either the mainstep or small timestep Aurora components must be used in DRAFT.  Both of these icons are shown below and can be found if the keyword ‘aurora’ is used to search the master library.


Using the Aurora Protocol to exchange data with and external device is an attractive option in cases where a lot a data needs to be moved in a short period of time.  The other IO cards and not ideal for such applications.  The data exchange between the RTDS Simulators and an Aurora-compatible device can be either unidirectional or bi-directional.  The number of signals exchanged and the direction of that exchange is generally application specific.

Examples of Interface options: (1/2) Unidirectional, (3) Bi-directional




Tighter Closed-Loop Performance using Sequence Numbers

For certain applications, data will be sent from the RTDS Simulator to an external device and the device will provide a response that should be read back into the simulation.  For such scenarios, we’ve introduced something called a sequence number that is useful for minimizing loop delays and improving closed-loop performance.

A sequence number is an integer that is appended to the package of data sent to an Aurora compatible device.  This integer is incremented every timestep.  When the sequence number option is enabled in the Aurora DRAFT component, the component will send out its package of data (including the sequence #) and then its execution is paused until the sequence number of an incoming data package matches the one sent out.  NOTE: The Aurora compatible device is expected to echo the sequence number it receives.

Use of sequence numbers makes it possible to send out data to external device using the Aurora protocol and then receive a response to that data within the same timestep.  This of course assumes the device is able to respond in significantly less time than a timestep.  Interfacing time delays can therefore be minimized.

*Due to performance constraints sequence numbers are not available for the small timestep Aurora component.

Aurora Interface Details

When generating the Xilinx IP Aurora core to connect to the NovaCor Aurora link, the following settings are required:

  • Aurora lanes : 1
  • Encoding: 8b/10b
  • Lane Width : design dependent
  • Interface : Framing
  • Dataflow Mode : Duplex
  • Flow Control : None
  • Line Rate : 2 Gbps
  • Scrambler/Descrambler: No
  • Little Endian Support: No
  • CRC: No

Additional Resources

A demo case that includes a reference FPGA design that can be loaded onto a Xilinx VC707 board is available to provide a starting point for customers wanting to use the Aurora protocol to communicate between the RTDS Simulator and an external device.

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