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Minispec

Minispec is a Hardware Description Language designed for teaching purposes. It is inspired by Bluespec, and the current implementation heavily leverages the Bluespec compiler, e.g., for type checking and to produce Verilog code. However, Minispec has a minimalistic feature set that seeks to reduce its learning curve. Key simplifications over Bluespec include:

  • Combinational logic: No typeclasses, numeric types, provisos, or pattern matching.

  • Sequential logic: Implicit interfaces, rules always fire every cycle (i.e., no synthesized schedulers), no Action or ActionValue methods, no <- assignments. Instead of Action/ActionValue methods, modules have inputs that rules read to change the module's state. This maps to a more structural design style of sequential logic than Bluespec, but with a simple execution model that avoids combinational cycles (unlike e.g., Verilog).

  • Parametric functions/modules/types with Integer or type parameters. No parametric (HM-style) type checking; instead, parametrics are elaborated as needed, then each instance is typechecked (similar to C++ templates).

Copyright & License

Copyright (C) 2019-2024 by Daniel Sanchez

Minispec is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.

Setup

Using a virtual machine (recommended): Install vagrant, then run vagrant up from the minispec root folder in your host. This will provision an Ubuntu 18.04 VM with all dependencies, and build the minispec compiler (msc). Then, run vagrant ssh to log into the VM.

The VM also installs Jupyter notebook with the Minispec kernel. Within the VM, run jupyter notebook --ip=0.0.0.0 to launch the notebook. You can access it from the host at http://127.0.0.1:8888 (port forwarding is already configured).

Dependencies:

  • Bluespec (bsc) version 2021.07 (build 4cac6eb). Note: It is important to use a compatible version of bsc. The Minispec compiler parses bsc output, which may change across versions. In practice, bsc output stays relatively stable across versions, so bsc-2016.07.beta1 and earlier open-source versions should work well. However, a different version may make make error reporting wonky.

  • A C++17 compiler (tested with gcc 8.2).

  • scons

  • xxd (standard in most Linux distributions).

  • ANTLR4 version 4.7 or above (tested with 4.7.2). This is now automatically downloaded and built (see SConstruct).

Build: Run scons -j16. This will produce msc (the Minispec compiler). msc is self-contained, you can copy it to your system path and use it as-is (run msc -h to see syntax and options).

Getting started

The Minispec language reference, at docs/reference, is the primary reference for the Minispec HDL. It describes the syntax and semantics of the language in detail, and illustrates their use. To build the reference, run:

make

The reference uses LaTeX, so you'll need a LaTeX distribution installed in your system (e.g., texlive).

examples/ contains several examples showcasing different aspects of Minispec. If you already know Bluespec, this should suffice to learn the language.

tests/ has compiler tests on non-working examples, meant to show error handling capabilities.

Finally, you may find it useful to check the grammar, at src/Minispec.g4.