Copyright(C) <2022> By gzzyyxh

Quafu

Quafu is a small soc which has a certain number of peripherals mounted on the wishbone bus, and its core is a 32-bit pipeline and sequential processor written in verilog(for running RVOS).

Overview

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Implemented ISAs

• RV32I

• Zicsr extension

• M extension

• Machine-level ISA

• ...

Features

• 32-bit.

• A load/store architecture.

• A pipelined architecture.

• Two modes(M & U).

• Support exception & interrupt

• Address space(wishbone B2):

                            |----0xffff_ffff----|
                            |                   |
                            |                   |
                            |                   |
                            |                   |
                            |                   |
                            |      unused       |
                            |                   |
                            |                   |
                            |                   |
                            |                   |
                            |                   |
                            |                   |
                            |-------------------| <--- 0x6000_0000
                            |        ram        |
                            |-------------------| <--- 0x5000_0000
                            |       clint       |
                            |-------------------| <--- 0x4000_0000
                            |        plic       |
                            |-------------------| <--- 0x3000_0000
                            |        gpio       |
                            |-------------------| <--- 0x2000_0000
                            |        uart       |
                            |-------------------| <--- 0x1000_0000
                            |        rom        |
                            |-------------------| <--- 0x0000_0000
  

• ...

Some extra features are planned for the future or under development

• branch predictor

• sdram controller

• flash controller

• spi controller

• supervisor modes

• RV32A support

• debug support(JTAG)

• Replace with AXI4

• MMU(Sv32 paging, for running xv6-riscv or others)

• ...

  Due to lack of time, I will continue to fix existing bugs and complete the above plans after the end of this semester (July and August 2022).

Geting Started

$sudo apt update

$sudo apt install build-essential gcc make perl dkms git gcc-riscv64-unknown-elf

$git clone https://github.com/gzzyyxh/Quafu

Synthesis via Quartus Prime

$cd cpu

You can also try compiling with open source tools such as iverilog and verilator, or other EDA software such as vivado.

Notice

• Your FPGA board must meet the following conditions:

  • logic elements >= 10,877

  • registers >= 4,155

The actual resource usage depends on EDA, and the above data is for reference only

• ROM and RAM are implemented using Altera IP core. You should pay attention to this.

$cd os

Compile RVOS

$make

Connecting serial port equipment

$sudo apt-get install minicom

$sudo minicom -s

Select serial port steup and configure serial device as the corresponding board, Bps/Par/Bits is 115200 8N1.

$sudo minicom

Then you will see

Refrences

• RISC-V Specification Volume 1, Unprivileged Spec v.

• RISC-V Specification Volume 2, Privileged Spec v.

• RISC-V-Reader-Chinese-v2p1

• RVOS

• xv6-riscv

• Computer Organization and Design RISC-V Edition

Sources

• emulsiV

• wishbone IP core

• UART IP core