SCR1 is an open-source RISC-V compatible MCU core, designed and maintained by Syntacore.

Key features

• RV32I|E[MC] ISA
• Machine privilege mode
• 2 to 4 stage pipeline
• 32-bit AXI4/AHB-Lite external interface
• Integrated IRQ controller and advanced debug
• Optimized for area and power
• Written in SystemVerilog
• Features a number of configurable parameters

For more information, see SCR1 External Architecture Specification and SCR1 User Manual.

Repository contents

Folder	Description
docs	SCR1 documentation
src	SCR1 RTL source and testbench files
sim	Tests and scripts for simulation
sim/tests/common	Common source files for tests
sim/tests/riscv_isa	Common source files for RISC-V ISA tests
sim/tests/riscv_compliance	Common source files for RISC-V Compliance tests
sim/tests/benchmarks/dhrystone21	Dhrystone 2.1 source files
sim/tests/benchmarks/coremark	Coremark platform specific source files
sim/tests/vectored_isr_sample	Simple test example for vectored interrupt mode
sim/tests/hello	Simple "hello" test
sim/verilator_wrap	Wrappers for Verilator simulation

Quick start guide

Prerequisites

RISC-V GCC toolchain is required to compile the software. You can use pre-built binaries or build the toolchain from scratch.

Using pre-built binary tools

Pre-built RISC-V GCC toolchain and OpenOCD binaries are available to download from http://syntacore.com/page/products/sw-tools. Download the archive (.tar.gz for Linux, .zip for Windows) for your platform, extract the archive to your preferred directory <GCC_INSTALL_PATH> and update the PATH environment variable as described in Setting environment variables section.

Building tools from source

You can build the RISC-V toolchain from sources.

Build procedure is verified at the Ubuntu 14.04 LTS and Ubuntu 16.04 LTS distributions.

sudo apt-get install autoconf automake libmpc-dev libmpfr-dev libgmp-dev gawk bison flex texinfo libtool make g++ pkg-config libexpat1-dev zlib1g-dev
git clone https://github.com/riscv/riscv-gnu-toolchain.git
cd riscv-gnu-toolchain
git checkout a71fc539850f8dacf232fc580743b946c376014b
git submodule update --init --recursive
./configure --prefix=<GCC_INSTALL_PATH> --enable-multilib
make

More detailed instructions on how to prepare and build the toolchain can be found in https://github.com/riscv/riscv-tools/blob/master/README.md.

Setting environment variables

Add the <GCC_INSTALL_PATH>/bin folder to the PATH environment variable:

export PATH=$PATH:<GCC_INSTALL_PATH>/bin

Included tests

By default, the simulation package includes the following tests:

• riscv_isa
• riscv_compliance
• coremark
• dhrystone21
• vectored_isr_sample
• hello

Some of the tests depend on the selected architecture (e.g. rv32i|e base, supported extensions or IPIC), and therefore can not be used for all core configurations (these are skipped automatically).

To run an arbitrary subset of tests, edit the tests target in the ./Makefile. Edit the ./sim/tests/riscv_isa/rv32_tests.inc to specify subset of RISC-V ISA tests.

Clone and prepare the RISC-V ISA tests

Clone RISC-V ISA tests to your preferred directory <RISCV_TESTS_PATH>

git clone https://github.com/riscv/riscv-tests
cd riscv-tests
git checkout a9433c4daa287fbe101025f2a079261a10149225

Set the $RISCV_TESTS environment variable accordingly:

export RISCV_TESTS=<RISCV_TESTS_PATH>

Clone RISC-V Compliance tests

Clone RISC-V Compliance tests to your preferred directory <RISCV_COMPLIANCE_TESTS_PATH>

git clone https://github.com/riscv/riscv-compliance
cd riscv-compliance
git checkout 9f280717f26f50833357db9bfb77a8c79835f162

Set the $RISCV_COMPLIANCE_TESTS environment variable accordingly:

export RISCV_COMPLIANCE_TESTS=<RISCV_COMPLIANCE_TESTS_PATH>

Prepare Coremark benchmark sources

Download CoreMark from EEMBC's web site and extract the archive from http://www.eembc.org/coremark/download.php, or clone from https://github.com/eembc/coremark

Copy the following files from into the sim/tests/benchmarks/coremark/src directory in this repository:

• core_main.c
• core_list_join.c
• coremark.h
• core_matrix.c
• core_state.c
• core_util.c

Running simulations

To build RTL, compile and run tests from the repo root folder:

make run_<SIMULATOR> BUS=<AHB, AXI> ARCH=<I, IM, IMC, IC, EM, EMC, EC> IPIC=<0, 1>

By default, the following options are used: BUS=AHB ARCH=IMC IPIC=0.

Build and run parameters can be configured in the ./Makefile.

After all the tests have finished, the results can be found in build/test_results.txt (default location).

Simulator selection

Currently supported simulators:

• run_modelsim - Mentor Graphics ModelSim
• run_vcs - Synopsys VCS
• run_ncsim - Cadence NCSim
• run_verilator - Verilator (version >= 4.0)
• run_verilator_wf - Verilator with waveforms support

Please note that RTL simulator executables should be in your PATH variable.

For option run_verilator_wf the waveform is generated for the last executed test and is stored in ./build/simx.vcd.

Architectural configuration

The RISC-V toolchain automatically uses the selected ARCH for code compilation.

Please make sure that architectural configuration selected for the SCR1 RTL matches the one used for tests compilation. SCR1 core parameters can be configured in ./src/includes/scr1_arch_description.svh

SDKs

There is number of FPGA-based SCR1 SDKs available.

Please, refer to the https://github.com/syntacore/scr1-sdk for more details.

Contacts

scr1@syntacore.com