RV-Processor

Work-in-progress

A simple FPGA based RISC-V processor built from scratch, with 5 stage pipelined architecture for learning purposes. For colorlight-i5 board.

1. Specs, features

• Piplined FETCH-DECODE-EXEC-MEMORY-WRITE, single core, 40MHz processor with RV32I ISA, without ecall, ebreak & fence
• Memory mapped peripherals through wishbone bus
  • SDRAM, with 8KB data cache
  • GPIO
  • HDMI (PoC)
• Clock correct verilator simulations

2. Features in progress

• Precise exception, and interrupt system
• Zicsr extension
• Formal verification
• Multiple functional units

DUE TO MANY DRASTIC CHANGES TO THE CURRENT PIPELINE IMPLEMENTATION ARE NEEDED IN ORDER TO SUPPORT PLANNED IMPROVEMENTS. THIS PROJECT IS NOW SUSPENDED. I WILL BE WORKING ON A OUT-OF-ORDER CORE WITH THOSE FEATURES ADDED. TBA.

3. Build instruction

Requirements

• Yosys commit 7c5dba8b7 (later commit using libmap-pass somehow break BRAM inferal)
• nextpnr
• prjtrellis
• verliator
• openFPGALoader
• RV32I compiler (change in Makefile)

Verilator build

• make test

Synthesizable build

• ROM=<ROMFILE.c> make bit