= Verilator
{c}
{wiki}
<Verilog> simulator that <transpiles> to <C++>.
One very good thing about this is that it makes it easy to create test cases directly in C++. You just supply inputs and clock the simulation directly in a C++ loop, then read outputs and assert them with `assert()`. And you can inspect variables by printing them or with GDB. This is infinitely more convenient than doing these IO-type tasks in <Verilog> itself.
Some simulation examples under \a[verilog].
First install <Verilator>. On <Ubuntu>:
``
sudo apt install verilator
``
Tested on Verilator 4.038, <Ubuntu 22.04>.
Run all examples, which have assertions in them:
``
cd verilator
make run
``
File structure is for example:
* \a[verilog/counter.v]: <Verilog> file
* \a[verilog/counter.cpp]: <C++> loop which clocks the design and runs tests with assertions on the outputs
* \a[verilog/counter.params]: <gcc> compilation flags for this example
* \a[verilog/counter_tb.v]: <Verilog> version of the <C++> test. Not used by Verilator. Verilator can't actually run out `_tb` files, because they do in Verilog IO things that we do better from <C++> in Verilator, so Verilator didn't bother implementing them. This is a good thing.
Example list:
* \a[verilog/negator.v], \a[verilog/negator.cpp]: the simplest non-identity combinatorial circuit!
* \a[verilog/counter.v], \a[verilog/counter.cpp]: sequential hello world. Synchronous active high reset with active high enable signal. Adapted from: http://www.asic-world.com/verilog/first1.html
* \a[verilog/subleq.v], \a[verilog/subleq.cpp]: subleq <one instruction set computer> with separated instruction and data RAMs