A directory of Western Digital’s RISC-V SweRV Cores
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Ajay Nath Ajay Nath
Ajay Nath and Ajay Nath Merged PR #12
Latest commit 5fb4941 Feb 19, 2019


SweRV RISC-V CoreTM from Western Digital

This repository contains the SweRV CoreTM design RTL


By contributing to this project, you agree that your contribution is governed by Apache-2.0.
Files under the tools directory may be available under a different license. Please review individual file for details.

Directory Structure

├── configs                 # Configurations Dir
│   └── snapshots           # Where generated configuration files are created
├── design                  # Design root dir
│   ├── dbg                 #   Debugger
│   ├── dec                 #   Decode, Registers and Exceptions
│   ├── dmi                 #   DMI block
│   ├── exu                 #   EXU (ALU/MUL/DIV)
│   ├── ifu                 #   Fetch & Branch Prediction
│   ├── include             
│   ├── lib
│   └── lsu                 #   Load/Store
├── docs
├── tools                   # Scripts/Makefiles
└── testbench               # (Very) simple testbench
    ├── asm                 #   Example assembly files
    └── hex                 #   Canned demo hex files


  • Verilator (3.926 or later) must be installed on the system
  • If adding/removing instructions, espresso must be installed (used by tools/coredecode)

Quickstart guide

  1. Clone the repository
  2. Setup RV_ROOT to point to the path in your local filesystem
  3. Determine your configuration {optional}
  4. Run make with tools/Makefile


SweRV can be configured by running the $RV_ROOT/configs/swerv.config script:

% $RV_ROOT/configs/swerv.config -h for detailed help options

For example to build with a DCCM of size 64 :

% $RV_ROOT/configs/swerv.config -dccm_size=64

This will update the default snapshot in $RV_ROOT/configs/snapshots/default/ with parameters for a 64K DCCM.

Add -snapshot=dccm64, for example, if you wish to name your build snapshot dccm64 and refer to it during the build.

This script derives the following consistent set of include files :

├── common_defines.vh                       # `defines for testbench or design
├── defines.h                               # #defines for C/assembly headers
├── pd_defines.vh                           # `defines for physical design
├── perl_configs.pl                         # Perl %configs hash for scripting
├── pic_ctrl_verilator_unroll.sv            # Unrolled verilog based on PIC size
├── pic_map_auto.h                          # PIC memory map based on configure size
└── whisper.json                            # JSON file for swerv-iss

Building a model

  1. Set the RV_ROOT environment variable to the root of the SweRV directory structure

    RV_ROOT = /path/to/swerv
    export RV_ROOT

  2. Create your configuration

    (Skip if default is sufficient)
    (Name your snapshot to distinguish it from the default. Without an explicit name, it will update/override the default snapshot)
    $RV_ROOT/configs/swerv.config [configuration options..] -snapshot=mybuild

    Snapshots are placed in $RV_ROOT/configs/snapshots/<snapshot name>/ directory

  3. Build with verilator:

    make -f $RV_ROOT/tools/Makefile verilator [snapshot=name]

This will create and populate the verilator obj_dir/ in the current work dir.

Other targets supported:

vcs  (Synopsys)  
irun (Cadence)  

Running a simple Hello World program (verilator)

RV_ROOT = /path/to/swerv
export RV_ROOT

make -f $RV_ROOT/tools/Makefile verilator-run

This will build a verilator model of SweRV with AHB-lite bus, and execute a short sequence of instructions that writes out "HELLO WORLD" to the bus.

You can re-execute using


Start of sim

Hello World from SweRV @WDC !!

Finished : minstret = 389, mcycle = 1658

End of sim

A vcd file sim.vcd is created which can be browsed by gtkwave or similar waveform viewers. trace_port.csv contains a log of the trace port.

The Makefile allows you to specify different assembly files from command line

make -f $RV_ROOT/tools/Makefile verilator-run ASM_TEST=my_hellow_world.s ASM_TEST_DIR=/path/to/dir

If you change only the assembly files, you do not need to rebuild verilator, just specify the target as program.hex :

make -f $RV_ROOT/tools/Makefile program.hex ASM_TEST=my_hello_world.s ASM_TEST_DIR=/path/to/dir

Western Digital, the Western Digital logo, G-Technology, SanDisk, Tegile, Upthere, WD, SweRV Core, SweRV ISS, and OmniXtend are registered trademarks or trademarks of Western Digital Corporation or its affiliates in the US and/or other countries. All other marks are the property of their respective owners.