Caravel Harness

Table of contents

• Overview
• Caravel Architecture
• Quick Start for User Projects
  • Digital User Project
  • Analog User Project
• Required Directory Structure
• Additional Material

Overview

Caravel is a template SoC for Google SKY130 free shuttles. The current SoC architecture is given below.

Datasheet and detailed documentation exist here

Caravel Architecture

Caravel is composed of three main sub-blocks: management area, storage area, and user project area.

Management Area --------------

The managment area includes a picorv32 based SoC that includes a number of periphrals like timers, uart, and gpio. The managemnt area runs firmware that can be used to:

• Configure User Project I/O pads
• Observe and control User Project signals (through on-chip logic analyzer probes)
• Control the User Project power supply

For a complete list of the SoC periphrals, check the memory map

Storage Area

The storage area is an auxiliary storage space for the managment SoC. It holds two dual port RAM blocks (1KB) generated by OpenRAM

The storage area is only accessible by the management SoC.

User Project Area --------------

This is the user space. It has a limited silicon area 2.92mm x 3.52mm as well as a fixed number of I/O pads 38 and power pads 4.

The user space has access to the following utilities provided by the management SoC:

• 38 IO Ports
• 128 Logic analyzer probes
• Wishbone port connection to the management SoC wishbone bus.

Quick Start for User Projects

Your area is the full user space, so feel free to add your project there or create a differnt macro and harden it seperately then insert it into the user_project_wrapper for digital projects or insert it into user_project_analog_wrapper for analog projects.

Digital User Project

If you are building a digital project for the user space, check a sample project at caravel_user_project.

If you will use OpenLANE to harden your design, go through the instructions in this README.

Digital user projects should adhere the following requirements:

• Top module is named user_project_wrapper
• The user_project_wrapper adheres to the pin order defined at Digital Wrapper Pin Order.
• The user_project_wrapper adheres to the fixed design configurations at Digital Wrapper Fixed Configuration.
• The user project repository adheres to the Required Directory Structure.

Analog User Project ------------------

If you are building an analog project for the user space, check a sample project at caravel_user_project_analog.

Analog user projects should adhere the following requirements:

• Top module is named user_analog_project_wrapper
• The user_analog_project_wrapper uses the empty analog wrapper.
• The user_analog_project_wrapper adheres to the same pin order and placement of the empty analog wrapper.

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IMPORTANT

Please make sure to run make compress before commiting anything to your repository. Avoid having 2 versions of the gds/user_project_wrapper.gds one compressed and the other not compressed.

For information on tooling and versioning, please refer to tool-versioning.rst.

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Required Directory Structure

• gds/ : includes all the gds files used or produced from the project.
• def : includes all the def files used or produced from the project.
• lef/ : includes all the lef files used or produced from the project.
• mag/ : includes all the mag files used or produced from the project.
• maglef : includes all the maglef files used or produced from the project.
• spi/lvs/ : includes all the spice files used or produced from the project.
• verilog/dv : includes all the simulation test benches and how to run them.
• verilog/gl/ : includes all the synthesized/elaborated netlists.
• verilog/rtl : includes all the Verilog RTLs and source files.
• openlane/<macro>/ : includes all configuration files used to run openlane on your project.
• info.yaml: includes all the info required in this example. Please make sure that you are pointing to an elaborated caravel netlist as well as a synthesized gate-level-netlist for the user_project_wrapper

NOTE:

If you're using openlane to harden your design, the verilog/gl def/ lef/ gds/ mag maglef directories should be automatically populated by openlane.

Additional Material ===============

MPW Two

• Open MPW Program - MPW-TWO Walkthrough
• MPW Two Shuttle Program

MPW One

• Caravel User Project Features -- What are the utilities provided by caravel to the user project ?
• Aboard Caravel -- How to integrate your design with Caravel?
• Things to Clarify About Caravel -- What versions to use with Caravel?
• 45 Chips in 30 Days: Open Source ASIC at its best!

Check mpw-one-final for the caravel used for the mpw-one tapeout.

> ⚠️ You don't need to integrate your design with Caravel GDS for MPW two. Running make ship is no longer required.