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Usage.md

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Using DFFRAM

DFFRAM is based around placeram, a Python module, and dffram.py, a Python application.

placeram is a custom placer using OpenROAD's Python interface. It places DFFRAM RAM/RF designs in a predetermined structure to avoid a lengthy and inefficient manual placement process for RAM.

dffram.py is an OpenLane-based flow that performs every step of hardening the RAM modules from elaboration to GDS-II stream out. It incorporates placeram.

Dependencies

  • macOS or Linux
  • The Nix Package Manager

Installing Nix

You can install Nix by following the instructions at https://nixos.org/download.html.

Or more simply, on Ubuntu, run the following in your Terminal:

sudo apt-get install -y curl
sh <(curl -L https://nixos.org/nix/install) --daemon --yes

On not systemd-based Linux systems, replace --daemon with --no-daemon.

Or on macOS:

sh <(curl -L https://nixos.org/nix/install) --yes

Enter your password if prompted. This hsould take around 5 minutes.

Make sure to close all terminals after you're done with this step.

Setting up the binary cache

Cachix allows the reproducible Nix builds to be stored on a cloud server so you do not have to build OpenLane's dependencies from scratch on every computer, which will take a long time.

First, you want to install Cachix by running the following in your terminal:

nix-env -f "<nixpkgs>" -iA cachix

Then set up the OpenLane binary cache as follows:

cachix use openlane

If cachix use openlane fails, re-run it as follows:

sudo env PATH="$PATH" cachix use openlane

Basic

git clone https://github.com/Cloud-V/DFFRAM 
cd DFFRAM
nix-shell
./dffram.py 8x32 # <8-2048>x<8-64>

Advanced

The compilation flow has four main arguments:

  • --pdk: The PDK
  • --scl: The Standard Cell Library
  • --building-blocks: The building blocks.
  • The Size (passed without a flag)

The building block full set pdk:scl:blocks corresponds to ./platforms/<pdk>/<scl>/_building_blocks/<name>/model.v. Building block sets are fundamentally similar with a number of exceptions, most importantly, the SCL used and supported sizes.

For example:

./dffram.py -p sky130A -s sky130_fd_sc_hd -b ram 8x32

Options

For a full list of options, please invoke:

./dffram.py --help

Secret Menu

DFFRAM supports a number of secret options you can use to further customize your experience. They are all passed as environment variables:

Variable Name Effect
FORCE_ACCEPT_SIZE DFFRAM checks that you are not using a size not officially marked supported as available by a certain building block set. If this environment variable is set to any value, the check is bypassed.
FORCE_DESIGN_NAME Design names are found based on the size. If you'd like to force dffram to use a specific design name instead, set this environment variable to that name.

Appendices