FPGA-based real-time Industrial Ethernet


August 12, 2019

Industrial automation demands high precise synchronization between PLCs and Slave devices. PROFINET-RT specification demands cycle time of 31.25us. We at ATOP Technologies, have used high speed XILINX ZYNQ FPGA to achieve the required cycle time. The data received from PLC is first processed by Ethernet MAC IP, the redundant and netload frames are discarded at MAC layer.

The received data are then processed on the Programmable logic side of FPGA. The processed data are then forwarded to next node which are connected in line topology. If the frame is intended to our node, the data is forwarded to Software stack or to the next node. The response frame received from stack is sent to PLC. Achieving the cycle time of 31.25us is practically possible using the Real time switch developed within FPGA.

ATOP Technologies, has developed the real time switch consisting of cut through. Cut-through mechanism is used to send the frames to next nodes. Store-and-forward switching techniques are out of scope of this paper. With in-house developed FPGA logic, ATOP Technologies has been able to implement 2-port real time switch. Frame received from PLC are expeditiously forwarded to the next downstream node. FPGA logic has helped to achieve required response time of PROFINET-RT protocol. The necessary software stack is ported on Processing Subsystem (PS) of FPGA. The Real time switch involves Frame filtering and identifying the Ethernet port details for each incoming frame. The complete logic is created as IP core, and can be easily ported on any of the XILINX SoC based devices. The protocol also adheres to IEC 61158-6-10.

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