Cocotb

A coroutine-based cosimulation testbench environment for verifying VHDL and SystemVerilog RTL using Python.

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Overview

Cocotb is an open-source framework that allows hardware verification engineers to write testbenches in Python. It co-simulates with traditional HDL simulators, allowing Python test code to interact with and verify VHDL or SystemVerilog designs. This approach leverages the power, flexibility, and extensive libraries of the Python ecosystem to create more powerful and maintainable testbenches.

✨ Key Features

  • Write testbenches in Python
  • Coroutine-based concurrency for readable test code
  • Interfaces with major VHDL and Verilog simulators (ModelSim, Verilator, etc.)
  • Automatic test discovery
  • Access to the full Python ecosystem (e.g., NumPy, Matplotlib) for stimulus generation and analysis
  • Open source and free to use (BSD License)

🎯 Key Differentiators

  • Leverages the highly productive Python language and its vast ecosystem
  • Simplifies testbench creation compared to the complexity of UVM
  • Simulator-agnostic, allowing tests to be run on different backends

Unique Value: Dramatically increases verification productivity and enables more powerful testing by using the modern, feature-rich Python ecosystem for testbench development.

🎯 Use Cases (5)

Functional verification of RTL modules Rapid testbench development for FPGAs Creating complex, software-driven test scenarios Automated regression testing in a CI/CD pipeline Replacing or augmenting SystemVerilog UVM testbenches

✅ Best For

  • FPGA design verification in both hobbyist and commercial projects
  • Testing of digital signal processing (DSP) blocks
  • Verification of processor cores and peripherals

💡 Check With Vendor

Verify these considerations match your specific requirements:

  • Users unfamiliar with Python
  • Environments where SystemVerilog UVM is a strict requirement and cannot be augmented

🏆 Alternatives

SystemVerilog (UVM) VHDL Verification Frameworks (OSVVM, UVVM)

Compared to SystemVerilog UVM, Cocotb is significantly easier to learn and faster to write, allowing engineers to focus on the verification problem rather than boilerplate code.

💻 Platforms

API (integrates with simulators on Windows, Linux, macOS)

✅ Offline Mode Available

🔌 Integrations

Aldec Active-HDL / Riviera-PRO Siemens ModelSim / Questa Verilator Icarus Verilog GHDL Cadence Xcelium Synopsys VCS

🛟 Support Options

  • ✓ Live Chat

💰 Pricing

Contact for pricing
Free Tier Available

Free tier: Cocotb is completely free and open source.

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