Subbus

Subbus is a term used in several domains to denote a secondary or subordinate bus within a larger system. In computing and embedded systems, a subbus provides a dedicated path for a subset of devices, separating slower or specialized peripherals from the main system bus. In audio engineering, a subbus (often called a subgroup or submix bus) routes multiple input channels to a shared processing or output path.

In computing, subbuses connect to a central processing unit or memory bus through a bridge, controller, or port expander. They may have their own signaling conventions, timing, and arbitration, allowing independent operation and simpler scalability. Devices on the subbus appear to a host system via a mapping of addresses or slots, and access is coordinated by a master on the main bus.

Historically, subbuses arose as systems grew to include more I/O and expansion capabilities. They enabled modular design and easier upgrades by isolating peripheral traffic from the core data path. Modern incarnations appear in microcontroller and SoC architectures as peripheral buses inside larger interconnects, as well as in software-defined or virtualized environments where a 'subbus' concept may describe a logical subdivision of an interconnect.

The exact implementation and terminology vary by manufacturer and domain, so readers encountering 'subbus' should consult the relevant hardware or system documentation for specifics. See also bus (computing), expansion bus, I/O subsystem.