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MBus is the next-generation interconnect that enables the millimeter-scale computing class.

MBus is a chip-to-chip bus designed for ultra-constrained systems. MBus is a multi-master bus supporting an arbitrary number of nodes, priority arbitration, efficient acknowledgements, and extensible addressing, with only four wires and consuming only 3.5 pJ/bit/chip.

MBus is power-aware, enabling the design of power-oblivious systems. Individual chips can fully power off and MBus will automatically take care of all the tricky details.

For more information visit

Repository Layout

This repository contains a reference MBus implementation and is the implementation used by the Michigan Micro Mote project at the University of Michigan. The MBus Verilog is considered stable and has been tested in dozens of fabricated chips.

  • releases: Packaged, formal releases of MBus. Use the latest release if you wish to include MBus in your own projects. The mbus_example directory is the template for creating new releases.
  • mbus: The development directory of MBus.
  • layer_controller: A higher-level interface that wraps the MBus frontend. The layer controller implements the MPQ protocol described in the MBus Specification and provides a register/memory interface to the rest of the chip.
    • The layer controller originally had separate implementations for simpler peripherals and complex chips (the CPU). As of v3, these are now consolidated into a unified design.

Copyright 2015 Regents of the University of Michigan

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

MBus Name and Logo

Use of the MBus name and logo are subject to the MBus Research End User License Agreement.

The agreement is available at


Reference implementation for MBus from the MBus team at the University of Michigan.







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