Simulation Environments

Pulpissimo supports simulation on various environments like commercial RTL simulators or Verilator. The scripts and source files for simulation are contained in this directory grouped in subdirectories by environment.

Supported Simulation Environments

Generic

The default generic SV testbench is a regular non-UVM SystemVerilog testbench to be simulated on conventional RTL simulators. There is a more complex testbench based on the legacy PULPissimo testebnch (tb_pulp.sv) and a simplified version to use as a template for your own TB (tb_pulp_simple.sv).

Verilator

TODO

Subdirectories

• tb: Contains the source-code like SystemVerilog, C (e.g. for DPI) or C++ (for Verilator) for the testebenches. The folder might also contains
• vip: Contains optional additionalverification IP for the environments that are not strictly necessary for the environment's TB.
• simulators: Contains the invocation scripts/makefiles to start the various simulation environments.

Simulation Environment Invocation

In order to streamline switching between different simulation environments and to allow for easy simulation invocation during software development for Pulpissimo, we define a standard interface to invoke a simulation interface based on environment variables.

Each simulation environment shall contain a Makefile with a target called run_sim to invoke the simulation. The run_sim target shall use the following mandatory environment variables (supplied by the user or the development SDK) to control simulation invocation:

• EXECUTABLE_PATH The absolute path to the compiled ELF executable to be run on PULPissimo.

Besides the mandatory environment variables, the following optional envionment variables shall be used for sim. environments supporting the relevant feature:

• GUI [0 or 1] For tools with a graphical user interface, this switch controls whether the user whishes to invoke the tool in GUI mode (1) or wants to simulate in console only mode.

• BATCH [0 or 1] If enabled, the run_sim target invocatoin shall exit with the simulated main functions return value as exit code. I.e. the value returned by the simulated firmware shall be returned by the the `run_sim** target as well. This simplifies CI testing using tests written in the form of C-applications. Simulation environments may expose optional custom environment variables to modify this behavior e.g. in order to fail test with a non-zero exit value based on the status of some optional verification IP.

Each simulation environment may expose additional environment variables for environment-specific behavior that cannot be easily supported by all environments.

Further, the simulation can be launched with built-in launchers configured in the pulp-runtime and pulp-sdk by setting up the appropriate environment variables, indicated at the end of the build flow. VSIM_PATH needs to point to the questasim build directory for PULPissimo, and VSIM needs to containt the same value as VSIM_BIN.

The run_sim target in the sim. environemts Makefile must be documented using Makefile docs (see ../../utils/utils.mk). All supported variables must be documented including the mandatory and optional variables defined above.