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README.md |
README.md
uriscv - Another tiny RISC-V implementation
Github: https://github.com/ultraembedded/core_uriscv
Simple, small, multi-cycle 32-bit RISC-V CPU implementation.
Most instructions take 2 cycles, apart from load/stores which take 4+ cycles (depending on memory latency), and division which can take up-to 34 cycles.
Features
- 32-bit RISC-V ISA CPU core.
- Support RISC-V’s integer (I), multiplication and division (M), and CSR instructions (Z) extensions (RV32IMZicsr).
- Implements base ISA spec v2.1 and parts of the privileged ISA spec v1.11.
- Supports machine mode privilege level only.
- Configurable support for exceptions, interrupts, timers, multiplication, division and error traps.
- Verified using random instruction sequences using cosimulation against C++ ISA model.
- Synthesizable Verilog 2001, Verilator and FPGA friendly.
- Coremark: 1.48 CoreMark/MHz (with HW mul/div)
- Dhrystone: 0.58 DMIPS/MHz ('legal compile options' / 337 instructions per iteration / with HW mul/div)
For my higher performance pipelined cores, see here:
- Coremark: 2.94CM/MHZ - http://github.com/ultraembedded/riscv
- Coremark: 4.1CM/MHz - http://github.com/ultraembedded/biriscv
Getting Started
Running Helloworld
To run a simple test image on the core RTL using Icarus Verilog;
# Install Icarus Verilog (Debian / Ubuntu / Linux Mint)
sudo apt-get install iverilog
# [or] Install Icarus Verilog (Redhat / Centos)
#sudo yum install iverilog
# Run a simple test image (test.elf)
cd demo
make
The expected output is;
Starting bench
VCD info: dumpfile waveform.vcd opened for output.
Test:
1. Initialised data
2. Multiply
3. Divide
4. Shift left
5. Shift right
6. Shift right arithmetic
7. Signed comparision
8. Word access
9. Byte access
10. Comparision
Configuration
Param Name | Valid Range | Description |
---|---|---|
SUPPORT_MUL | 1/0 | Enable multiplication instructions. |
SUPPORT_DIV | 1/0 | Enable division instructions. |
SUPPORT_CSR | 1/0 | Global enable for CSR/trap/interrupt handling. |
SUPPORT_TRAP_LSU_ALIGN | 1/0 | Enable unaligned memory load / store exception. |
SUPPORT_MTVEC | 1/0 | Configurable exception entry address. |
SUPPORT_MTVAL | 1/0 | Support MTVAL CSR (holds bad addr / opcode). |
SUPPORT_MIP_MIE | 1/0 | Support MIE and MIP CSR registers. |
SUPPORT_MSCRATCH | 1/0 | Support MSCRATCH CSR registers (SW read/write). |
SUPPORT_MCYCLE | 1/0 | Support cycle counter / rdtime. |
SUPPORT_MTIMECMP | 1/0 | Non-std - support timer compare interrupt. |
SUPPORT_TRAP_INVALID_OPC | 1/0 | Fault on invalid opcodes (enable SW emulation). |
SUPPORT_BRAM_REGFILE | 1/0 | FPGA BlockRAM friendly reg file (inst take 1 cycle longer). |
ISR_VECTOR | 'h0-FFFFFFFF | ISR addr = reset_vector + ISR_VECTOR (SUPPORT_MTVEC = 0). |