Riscduino Quad Risc Core SOC


Permission to use, copy, modify, and/or distribute this soc for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOC IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOC INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOC.

Table of contents

• Overview
• Riscduino Block Diagram
• Key Feature
• Sub IP Feature
• SOC Memory Map
• Pin Mapping
• Repository contents
• Prerequisites
• Tests preparation
  • Running Simuation
• Tool sets
• Documentation

Overview

Riscduino is a Quad 32 bit RISC V based SOC design pin compatible to arudino platform and this soc targetted for efabless Shuttle program. This project uses only open source tool set for simulation,synthesis and backend tools. The SOC flow follow the openlane methodology and SOC environment is compatible with efabless/carvel methodology.

Riscduino Block Diagram

Key features

    * Open sourced under Apache-2.0 License (see LICENSE file) - unrestricted commercial use allowed.
    * Quad Core  32 Bit RISC-V core
    * 2KB SRAM for instruction cache 
    * 2KB SRAM for data cache
    * 2KB SRAM for Tightly coupled memory - For Data Memory
    * Quad SPI Master
    * UART with 16Byte FIFO
    * USB 1.1 Host
    * I2C Master
    * UART Master
    * Simple SPI Master
    * 6 Channel ADC (in Progress)
    * 6 PWM
    * Pin Compatbible to arudino uno
    * Wishbone compatible design
    * Written in System Verilog
    * Open-source tool set
       * simulation - iverilog
       * synthesis  - yosys
       * backend/sta - openlane tool set
    * Verification suite provided.

SOC Pin Mapping

Carvel SOC provides 38 GPIO pins for user functionality. Riscduino SOC GPIO Pin Mapping as follows vs ATMEGA328 and Arudino

RISC V Core

Riscduino SOC Integrated Quad 32 Bits RISC V core. Initial version of Single core RISC-V core is picked from Syntacore SCR1 (https://github.com/syntacore/scr1)

RISC V core customization for Riscduino SOC

Following Design changes are done on the basic version of syntacore RISC core

   * Some of the sv syntex are changed to standard verilog format to make compatibile with opensource tool iverilog & yosys
   * local Instruction Memory is increased from 4 to 8 location
   * Instruction Request are changed from Single word to 4 Word Burst
   * Multiplication and Divsion are changed to improve timing
   * Additional pipe line stages added to improve the RISC timing closure near to 50Mhz
   * 2KB instruction cache 
   * 2KB data cache
   * Additional router are added towards instruction cache
   * Additional router are added towards data cache
   * Quad core related changes
   * Modified AXI/AHB interface to wishbone interface for instruction and data memory interface

Block Diagram

RISC V Core Key feature

   * RV32I or RV32E ISA base + optional RVM and RVC standard extensions
   * Machine privilege mode only
   * 2 to 5 stage pipeline
   * 2KB icache
   * 2KB dcache
   * Optional Integrated Programmable Interrupt Controller with 16 IRQ lines
   * Optional RISC-V Debug subsystem with JTAG interface
   * Optional on-chip Tightly-Coupled Memory

SOC Memory Map

SOC Size

SOC Register Map

Register Map: Wishbone HOST

Register: GLBL_CTRL

Register: BANK_CTRL

Register: CLK_SKEW_CTRL1

Register Map: SPI MASTER

Register: GLBL_CTRL

Register: DMEM_CTRL1

Register: DMEM_CTRL2

Register: IMEM_CTRL1

Register: IMEM_CTRL2

Register: IMEM_ADDR

Register: IMEM_WDATA

Register: IMEM_RDATA

Register: SPI_STATUS

Register Map: Global Register

Register: RISC_FUSE

Register: INTR_CTRL

Repository contents

|verilog
|   ├─  rtl
|   |     |-  syntacore
|   |     |     |─  scr1
|   |     |     |    ├─ **docs**                           | **SCR1 documentation**
|   |     |     |    |      ├─ scr1_eas.pdf                | SCR1 External Architecture Specification
|   |     |     |    |      └─ scr1_um.pdf                 | SCR1 User Manual
|   |     |     |    |─  **src**                           | **SCR1 RTL source and testbench files**
|   |     |     |    |   ├─ includes                       | Header files
|   |     |     |    |   ├─ core                           | Core top source files
|   |     |     |    |   ├─ top                            | Cluster source files
|   |     |     |    |─  **synth**                         | **SCR1 RTL Synthesis files **
|   |     |- Qspi_master
|   |     |     |- src                                     | Qard SPI Master Source files
|   |     |-wb_interconnect
|   |     |     |- src                                     | 3x4 Wishbone Interconnect
|   |     |- digital_core
|   |     |     |- src                                     | Digital core Source files
|   |     |- lib                                           | common library source files
|   |- dv
|   |   |- la_test1                                        | carevel LA test
|   |   |- risc_boot                                       | user core risc boot test
|   |   |- wb_port                                         | user wishbone test
|   |   |- user_risc_boot                                  | user standalone test without carevel soc
|   |- gl                                                  | ** GLS Source files **
|
|- openlane
    |- spi_master                                          | spi_master openlane scripts   
    |- syntacore                                           | Risc Core openlane scripts   
    |- user_project_wrapper                                | carvel user project wrapper 

Prerequisites

• Docker (ensure docker daemon is running) -- tested with version 19.03.12, but any recent version should suffice.

Step-1: Docker in ubuntu 20.04 version

   sudo apt update
   sudo apt-get install apt-transport-https curl rtificates -agent software-properties-common
   curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
   sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu focal stable"
   sudo apt update
   apt-cache policy docker-ce
   sudo apt install docker-ce

   #Add User Name to docker
   sudo usermod -aG docker <your user name>
   # Reboot the system to enable the docker setup

Step-2: Update the Submodule, To to project area

   git submodule init
   git submodule update

Step-3: clone Openlane scripts under workarea

   git clone https://github.com/The-OpenROAD-Project/OpenLane.git

Step-4: add Environment setting

    export CARAVEL_ROOT=<Carvel Installed Path>
    export OPENLANE_ROOT=<OpenLane Installed Path>
    export OPENLANE_IMAGE_NAME=efabless/openlane:latest
    export PDK_ROOT=<PDK Installed PATH>
    export PDK_PATH=<PDK Install Path>/sky130A

Step-5: To install the PDK

   source ~/.bashrc
   cd OpenLane
   make pdk

Tests preparation

The simulation package includes the following tests:

• risc_boot - Simple User Risc core boot
• wb_port - User Wishbone validation
• user_risc_boot - Standalone User Risc core boot
• user_mbist_test1 - Standalone MBIST test
• user_spi - Standalone SPI test
• user_i2c - Standalone I2C test
• user_risc_soft_boot - Standalone Risc with SRAM as Boot

Running Simulation

Examples:

    make verify-wb_port  
    make verify-risc_boot
    make verify-user_uart
    make verify-user_spi
    make verify-user_i2cm
    make verify-user_risc_boot
    make verify-wb_port SIM=RTL DUMP=OFF
    make verify-wb_port SIM=RTL DUMP=ON
    make verify-riscv_regress

Tool Sets

Riscduino Soc flow uses Openlane tool sets.

1. Synthesis
   1. yosys - Performs RTL synthesis
   2. abc - Performs technology mapping
   3. OpenSTA - Pefroms static timing analysis on the resulting netlist to generate timing reports
2. Floorplan and PDN
   1. init_fp - Defines the core area for the macro as well as the rows (used for placement) and the tracks (used for routing)
   2. ioplacer - Places the macro input and output ports
   3. pdn - Generates the power distribution network
   4. tapcell - Inserts welltap and decap cells in the floorplan
3. Placement
   1. RePLace - Performs global placement
   2. Resizer - Performs optional optimizations on the design
   3. OpenPhySyn - Performs timing optimizations on the design
   4. OpenDP - Perfroms detailed placement to legalize the globally placed components
4. CTS
   1. TritonCTS - Synthesizes the clock distribution network (the clock tree)
5. Routing
   1. FastRoute - Performs global routing to generate a guide file for the detailed router
   2. CU-GR - Another option for performing global routing.
   3. TritonRoute - Performs detailed routing
   4. SPEF-Extractor - Performs SPEF extraction
6. GDSII Generation
   1. Magic - Streams out the final GDSII layout file from the routed def
   2. Klayout - Streams out the final GDSII layout file from the routed def as a back-up
7. Checks
   1. Magic - Performs DRC Checks & Antenna Checks
   2. Klayout - Performs DRC Checks
   3. Netgen - Performs LVS Checks
   4. CVC - Performs Circuit Validity Checks

Contacts

Report an issue: https://github.com/dineshannayya/riscduino/issues

Documentation

• Syntacore Link - https://github.com/syntacore/scr1