Simulating Verilog
Contents
Introduction
This section will briefly talk about how to simulate Verilog. You can simulate Verilog that is either behavioral, gate-level, or back-annotated (with delays). Behavioral and gate-level are done in the same way, but back annotate requires an extra system call in your Verilog.
The first thing I recommend that you do is to create a "project.f" file that is just a list of all of your Verilog files. Like this:
sram.v sram_tb.v
Running Verilog
You can use two different Verilog simulators: ncverilog ("ncverilog") or verilog-XL ("verilog"). There is also a 3rd GNU simulator called Icarus Verilog that you can install on your own computer.
ncverilog
Simply run:
ncverilog -f project.f
Look for any warnings or errors. At the end of the output, you should see:
Simulation complete via $finish(1) at time 10 US + 0 ./sram_tb.v:64 $finish(); ncsim> exit
If you want to view the outputs in a GUI, you can run:
ncverilog -f project.f +gui
This will compile the verilog and run SimVision. There is more on SimVision in the Advanced Testbenches tutorial.
You can also put these extra arguments in the project.f file.
Verilog-XL
Icarus Verilog
Simulating Verilog in Ultrasim
For non-digital simulations, you can simulate a structural Verilog netlist in Ultrasim as well. However, you need to supply the spice subcircuits of the library:
/mada/software/techfiles/osu_soc_v2.7/cadence/lib/tsmc025/signalstorm/osu025_stdcells.sp
Back-Annotation
In order to back-annotate, you should output an SDF file from either Synopsys Design Compiler (before physical design) or from SoC encounter. Each SDF format is sometimes different, so you may have to hack it to get it to work. Common incompatibilities are the dilimiting characters in hierarchical names, for example. Carefully watch the warnings!
The system call to back-annotate is like this:
initial begin
$sdf_annotate("gate/lfsr-final.sdf", l0);
end
where lfsr.sdf is the SDF file and l0 is the instance name of the top module that you synthesized. Note that you should not be using your unsynthesized verilog now. Use the output from synthesis in the file, gate/lfsr-final.v, along with your original testbench.
