Feature Covered - 2025.1 English - UG937

1. Detection of designs with PAM4 signals, designs instantiating GTM_DUAL and automatic generation bypass module (xil_dut_bypass).
2. Simple sanity check for the design that should instantiate bypass module.
3. A mechanism to view PAM4 signals in Waveform Viewer for XSim users.
4. Provide a way to generate a bypass module for export simulation flow.

In this tutorial, you would generate a GTM-Wizard example design, which uses a PAM4 signal. To generate that, follow the steps below:

1. Create a project in Vivado 2025.x without adding a source/constraint file. Click Create project, and then click Next until the Default Part page is displayed.
2. In the Default Part page, select Virtex UltraScale+ 58G and select parts as shown in the following figure, and click Next.
   
3. Check the summary report and click Finish.
   
4. Under Project Manager, click on IP Catalog and search for gtm_wizard and then double-click Virtex UltraScale+ FPGAs Transceivers Wizard.
   
5. Click OK on default configuration and click Skip on Generate Output Product dialog box.
   
6. On Sources window, right-click the generated XCI file, click Open IP Example Design, and specify the location.
   

   At this stage, you have an example ready to run the simulation.

Before heading towards simulation, here are a few things from the PAM4 point of view:

1. xil_dut_bypass module definition is generated on runtime by the tool that contains a hierarchical reference to GTM_DUAL.
   
2. This xil_dut_bypass module generation is controlled by the Configure Design for Hierarchical Access option, which is set by default.
   
   Note: For old behavior, uncheck Configure Design for Hierarchical Access.

   Once the design is created, you can run it either through launch_simulation or export_simulation.

Launch_simulation

1. Click Run Behavioral Simulation. This will run the simulation with Vivado Simulator.
   
2. Once the snapshot is created and loaded, the simulation will stop after 1000 ns. Let us look at xil_dut_bypass definition. Double-click xil_dut_bypass in the Scope window to see the source file. Note the hierarchical reference from the top module to the leaf-level instance.
   
3. Right-click xil_dut_bypass and add to waveform.
   
4. Click Restart and run all.
5. Once the simulation is complete, section all signals of xil_dut_bypass in the waveform, right click, and select Waveform Style to Analog.
   
6. Go to analog setting under waveform style and change the value like below for better waveform.
   
7. Observe the analog value of signals.
   
   Note: For running the same design with third-party simulators, refer to Vivado Design Suite User Guide: Logic Simulation (UG900).

Export_simulation

The following are the two flows for export simulation:

Export simulation with xil_dut_bypass generated

1. Invoke command export_simulation -simulator xsim -generate_hier_access on Vivado IDE.

   This generates scripts in <your_local_path>/export_sim/xsim.

2. In the generated vlog.prj, observe xil_dut_bypass.sv. This is because launch_simulation has generated and added this as part of the project.
   
   
3. Invoke gtm_wizard_ultrascale_0_example_top_sim.sh it runs the simulation. If you want to run in GUI mode, add -gui to xsim command of else part.
4. Follow step-3 to step-7 under launch_simulation and you will be able to see the same waveform/output as launch_simulation.

Export simulation without xil_dut_bypass

1. Invoke gtm_wizard_ultrascale_0_example_top_sim.sh -gen_bypass.
2. It runs the simulation for delta time unit and generate hierarchical path in the log file.
3. In generated simulate.log, note down the entry xilinx_hier_bypass_ports:gtm_wizard_ultrascale_0_example_top_sim.u_e….
4. Generate xil_dut_bypass.sv by invoking generate_hier_access -log ./simulate.log on Vivado Tcl Console.
5. Observe xil_dut_bypass.sv generate in current directory.
6. Add this xil_dut_bypass.sv in vlog.prj as sv xil_defaultlib ./xil_dut_bypass.sv.
7. Invoke gtm_wizard_ultrascale_0_example_top_sim.sh it runs simulation. If you want to run in GUI mode, add -gui to xsim command of else part.
   
   
8. Follow step-3 to step-7 under launch_simulation and you can see same waveform/output as launch_simulation.

Generating xil_dut_bypass for non-vivado project

1. Create compile order of the design (<design>.prj).
2. Execute XSim simulator tools to generate the simulator log file:
   1. xelab -prj <design>.prj -top <testbench-top>.
   2. xsim -R <testbench-top> --testplusarg GEN_BYPASS.
3. Verify <simulator>.log file generated and that it contains the xilinx_hier_bypass_ports string with the hierarchical path information. For example:

   xilinx_hier_bypass_ports:tb.dut_i.gtmWiz_00.gtm_i in:integer:in1:in_var1 in:integer:in2:in_var2 
   out:integer:out1:out_var1 out:integer:out2:out_var2

4. Download generate_hier_access.tcl utility from GitHub:

   wget https://raw.githubusercontent.com/Xilinx/XilinxTclStore/2020.1-dev/tclapp/xilinx/projutils/generate_hier_access.tcl

5. Execute generate_hier_access.tcl to generate the sources for hierarchical access simulation:
   1. # /usr/bin/tclsh.
   2. source generate_hier_access.tcl.
   3. generate_hier_access -bypass dut_bypass -testbench <module> -directory <path> -log <simulator>.log. Instantiate this dut_bypass in test bench with proper connection.
6. Add <path>/dut_bypass.sv to <design>.prj.
7. Run simulator tools to simulate the design in <design>.prj.