Answer: Bus Arbitration - Definition

Bus Arbitration is the process of resolving contention when multiple bus masters (CPU, DMA controller, processors in multiprocessor system, I/O controllers) simultaneously request control of the system bus. Since only one master can drive the bus at a time, an arbiter decides priority and grants bus access.

Need: Prevents collision and ensures orderly transfer.

Approaches:

1. Centralized Arbitration: Single hardware arbiter (e.g., priority encoder) grants bus via Bus Request ($BR$) / Bus Grant ($BG$) daisy-chain or independent requests.
2. Distributed Arbitration: Each master has its own arbitration logic and decides collectively (e.g., self-selection).

Common schemes: Daisy chaining, Polling, Independent Request (Parallel arbitration). Priority may be fixed, rotating, or dynamic.

In short, bus arbitration = mechanism to select one master among contenders to become next bus master.