25G Ethernet Design Example User Guide

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UG-20048 | 2017.11.08

25GbE Quick Start Guide

The 25GbE IP core provides a simulation testbench and a hardware design example that supports compilation and hardware testing. When you generate the design example, the parameter editor automatically creates the files necessary to simulate, compile, and test the design in hardware. You can download the compiled hardware design to an Arria 10 GT device.

Note: This design example targets the Arria 10 GT device and requires a 25G retimer. Please contact your Intel FPGA representative to inquire about a platform suitable to run this hardware example. In some cases a loan of appropriate hardware may be available.

In addition, Intel provides a compilation-only example project that you can use to quickly estimate IP core area and timing.

Figure 1. Design Example Usage

Design Example Directory Structure

Figure 2. 25GbE Design Example Directory Structure

The hardware configuration and test files (the hardware design example) are located in <design_example_dir>/hardware_test_design. The simulation files (testbench for simulation only) are located in <design_example_dir>/example_testbench.The compilation-only design example is located in <design_example_dir>/compilation_test_design.

Simulation Design Example Components

Figure 3. 25GbE Simulation Design Example Block Diagram

The simulation design example top-level test file is basic_avl_tb_top.sv This file instantiates and connects an ATX PLL. It includes a task, send_packets_25g_avl, to send and receive 10 packets.

Table 1. 25GbE IP Core Testbench File Descriptions
File Name	Description
Testbench and Simulation Files
basic_avl_tb_top.sv	Top-level testbench file. The testbench instantiates the DUT and runs Verilog HDL tasks to generate and accept packets.
Testbench Scripts
run_vsim.do	The ModelSim script to run the testbench.
run_vcs.sh	The Synopsys VCS script to run the testbench.
run_ncsim.sh	The Cadence NCSim script to run the testbench.

Hardware Design Example Components

Figure 4. 25GbE Hardware Design Example High Level Block Diagram

The 25GbE hardware design example includes the following components:

25GbE IP core.
Client logic that coordinates the programming of the IP core and packet generation.
ATX PLL to drive the device transceiver channel.
JTAG controller that communicates with the System Console. You communicate with the client logic through the System Console.

Table 2. 25GbE IP Core Hardware Design Example File Descriptions
File Names	Description
eth_ex_25g.qpf	Quartus Prime project file
eth_ex_25g.qsf	Quartus project settings file
eth_ex_25g.v	Top-level Verilog HDL design example file
common/	Hardware design example support files
hwtest/main.tcl	Main file for accessing System Console

Generating the Design Example

Figure 5. Procedure

Figure 6. Example Design Tab in the 25GbE Parameter Editor

Follow these steps to generate the hardware design example and testbench:

In the Quartus^® Prime software, in the IP Catalog (Tools > IP Catalog), select the Arria 10 target device family.
In the IP Catalog, locate and select 25G Ethernet. The New IP Variation window appears.
Specify a top-level name for your IP variation and click OK. The parameter editor adds the top-level .qsys (in Quartus^® Prime Standard Edition) or .ip (in Quartus^® Prime Pro Edition) file to the current project automatically. If you are prompted to manually add the .qsys or .ip file to the project, click Project > Add/Remove Files in Project to add the file.
You must select a specific Arria 10 device in the Device field, or keep the default device the Quartus Prime software proposes.
Note: The hardware design example overwrites the selection with the device on the target board. You specify the target board from the menu of design example options in the Example Design tab (Step 8).
Click OK. The parameter editor appears.
On the IP tab, specify the parameters for your IP core variation.
On the Example Design tab, for Example Design Files, select the Simulation option to generate the testbench, and select the Synthesis option to generate the hardware design example. Only Verilog HDL files are generated.
For Hardware Board select the Arria 10 GX Transceiver Signal Integrity Development Kit.
Note: Contact your Intel FPGA representative for information about a platform suitable to run this hardware example.
Click the Generate Example Design button. The Select Example Design Directory window appears.
If you wish to modify the design example directory path or name from the defaults displayed (alt_e25_0_example_design ), browse to the new path and type the new design example directory name (<design_example_dir>).
Click OK.
Refer to the KDB Answer How do I compensate for the jitter of PLL cascading or non-dedicated clock path for Arria 10 PLL reference clock? for a workaround you should apply in the hardware_test_design directory in the .sdc file.
Note: You must consult this KDB Answer because the RX path in the 25GbE IP core includes cascaded PLLs. Therefore, the IP core clocks might experience additional jitter in Arria 10 devices. This KDB Answer clarifies the software releases in which the workaround is necessary.

Simulating the 25GbE Design Example Testbench

Figure 7. Procedure

Follow these steps to simulate the testbench:

Change to the testbench simulation directory <design_example_dir>/example_testbench.
Run the simulation script for the supported simulator of your choice. The script compiles and runs the testbench in the simulator. Refer to the table "Steps to Simulate the Testbench".

Analyze the results. The successful testbench sends ten packets, receives ten packets, and displays "Testbench complete."

Table 3. Steps to Simulate the Testbench
Simulator	Instructions
ModelSim	In the command line, type vsim -do run_vsim.do If you prefer to simulate without bringing up the ModelSim GUI, type vsim -c -do run_vsim.do Note: The ModelSim-AE and ModelSim-ASE simulators do not have the capacity to simulate this IP core. You must use another supported ModelSim simulator such as ModelSim SE.
NCSim	In the command line, type sh run_ncsim.sh
VCS	In the command line, type sh run_vcs.sh

The successful test run displays output confirming the following behavior:

Waiting for RX clock to settle
Printing PHY status
Sending 10 packets
Receiving 10 packets
Displaying "Testbench complete."

The following sample output illustrates a successful simulation test run:

#Ref clock is run at 625 MHz so whole numbers can used for all clock periods.
#Multiply reported frequencies by 33/32 to get actual clock frequencies.
#Waiting for RX alignment
#RX deskew locked
#RX lane alignment locked
#TX enabled
#**Sending Packet    1...
#**Sending Packet    2...
#**Sending Packet    3...
#**Sending Packet    4...
#**Sending Packet    5...
#**Sending Packet    6...
#**Sending Packet    7...
#**Received Packet   1...
#**Sending Packet    8...
#**Received Packet   2...
#**Sending Packet    9...
#**Received Packet   3...
#**Sending Packet    10...
#**Received Packet   4...
#**Received Packet   5...
#**Received Packet   6...
#**Received Packet   7...
#**Received Packet   8...
#**Received Packet   9...
#**Received Packet   10... 
#**
#** Testbench complete.
#**
#*****************************************

Compiling and Configuring the Design Example in Hardware

To compile the hardware design example and configure it on your Arria 10 GT device, follow these steps:

Ensure hardware design example generation is complete.
In the Quartus^® Prime software, open the Quartus^® Prime project <design_example_dir>/hardware_test_design/eth_ex_25g.qpf.
Before compiling, ensure you have implemented the workaround from the KDB Answer How do I compensate for the jitter of PLL cascading or non-dedicated clock path for Arria 10 PLL reference clock? if relevant for your software release.
On the Processing menu, click Start Compilation.
After you generate a SRAM object file .sof, follow these steps to program the hardware design example on the Arria 10 device:
1. On the Tools menu, click Programmer.
2. In the Programmer, click Hardware Setup.
3. Select a programming device.
4. Select and add the Arria 10 GT board with 25G retimer to your Quartus^® Prime session.
5. Ensure that Mode is set to JTAG.
6. Select the Arria 10 device and click Add Device. The Programmer displays a block diagram of the connections between the devices on your board.
7. In the row with your .sof, check the box for the .sof.
8. Check the box in the Program/Configure column.
9. Click Start.

Note: This design example targets the Arria 10 GT device. Please contact your Intel FPGA representative to inquire about a platform suitable to run this hardware example

Testing the 25GbE Hardware Design Example

After you compile the 25GbE IP core design example and configure it on your Arria 10 GT device, you can use the System Console to program the IP core and its embedded Native PHY IP core registers.

To turn on the System Console and test the hardware design example, follow these steps:

After the hardware design example is configured on the Arria 10 device, in the Quartus^® Prime software, on the Tools menu, click System Debugging Tools > System Console.
In the Tcl Console pane, type cd hwtest to change directory to <design_example_dir>/hardware_test_design/hwtest.
Type source main.tcl to open a connection to the JTAG master.

You can program the IP core with the following design example commands:

chkphy_status: Displays the clock frequencies and PHY lock status.
chkmac_stats: Displays the values in the MAC statistics counters.
clear_all_stats: Clears the IP core statistics counters.
start_gen: Starts the packet generator.
stop_gen: Stops the packet generator.
loop_on: Turns on internal serial loopback
loop_off: Turns off internal serial loopback.
reg_read <addr>: Returns the IP core register value at <addr>.
reg_write <addr> <data>: Writes <data> to the IP core register at address <addr>.

Design Example Description

The design example demonstrates the functions of the 25GbE IP core. You can generate the design from the Example Design tab in the 25GbE parameter editor.

To generate the design example, you must first set the parameter values for the IP core variation you intend to generate in your end product. Generating the design example creates a copy of the IP core; the testbench and hardware design example use this variation as the DUT. If you do not set the parameter values for the DUT to match the parameter values in your end product, the design example you generate does not exercise the IP core variation you intend.

Design Example Behavior

The testbench sends traffic through the IP core, exercising the transmit side and receive side of the IP core. In the hardware design example, you can program the IP core in internal serial loopback mode and generate traffic on the transmit side that loops back through the receive side.

Design Example Interface Signals

The 25GbE testbench is self-contained and does not require you to drive any input signals.

Table 4. 25GbE Hardware Design Example Interface Signals
Signal	Direction	Comments
`clk50`	Input	Drive at 50 MHz. The intent is to drive this from a 50 Mhz oscillator on the board.
`clk_ref`	Input	Drive at 644.53125 MHz.
`cpu_resetn`	Input	Resets the IP core. Active low. Drives the global hard reset `csr_reset_n` to the IP core.
`tx_serial`	Output	Transceiver PHY output serial data.
`rx_serial`	Input	Transceiver PHY input serial data.
`user_led[7:0]`	Output	Status signals. The hardware design example connects these bits to drive LEDs on the target board.

25GbE Design Example Registers

Table 5. 25GbE Hardware Design Example Register Map. Lists the memory mapped register ranges for the hardware design example. You access these registers with the `reg_read` and `reg_write` functions in the System Console.
Word Offset	Register Category
0x300–0xDFF	25GbE IP core registers.
0x4000–0x4C00	Arria 10 dynamic reconfiguration registers. Register base address is 0x4000.

Document Revision History

Table 6. 25G Ethernet Design Example User Guide Revision History
Date	Release	Changes
2017.11.08	16.1	Added link to KDB Answer that provides workaround for potential jitter on Arria^® 10 devices due to cascading ATX PLLs in the IP core. Refer to Generating the Design Example and Compiling and Configuring the Design Example in Hardware. Note: This design example user guide has not been updated to reflect minor changes in design generation in Quartus^® Prime releases later than the Quartus^® Prime software release v16.1.
2016.10.31	16.1	Initial release.