Centralised Arbitration
Centralized arbitration refers to a method of resolving conflicts or prioritizing requests in a centralized system. In this context, arbitration refers to the process of determining which device or component gets access to the shared resources.

Role of BUS master
The BUS master is a device or component that controls the flow of data and commands on the BUS. It is responsible for initiating and managing data transfers between devices connected to the BUS. The BUS master takes control of the BUS during arbitration and decides which device or component can access the BUS and for how long.

Processor in Centralised Arbitration
In a centralized arbitration system, the processor is one of the potential BUS masters. The processor is the main component of a computer system that performs computations, executes instructions, and manages the overall operation of the system. In the context of arbitration, the processor can act as a BUS master and control the BUS to access shared resources.

DMA Controller in Centralised Arbitration
A DMA (Direct Memory Access) controller is another potential BUS master in centralized arbitration. The DMA controller is responsible for managing data transfers between peripherals and memory without involving the processor. It can also take control of the BUS during arbitration and prioritize DMA requests from different peripherals.

Both Processor and DMA Controller as BUS masters
In the context of centralized arbitration, both the processor and DMA controller can act as BUS masters. They have the authority to request access to the BUS and control the flow of data and commands. Depending on the arbitration algorithm implemented, the processor and DMA controller may compete for BUS access and prioritize their requests based on predefined rules.

Summary
In summary, in centralized arbitration, both the processor and DMA controller can act as BUS masters. They have the authority to initiate and manage data transfers by controlling the BUS. The processor performs computations and manages the overall operation of the system, while the DMA controller is responsible for managing data transfers between peripherals and memory. Depending on the arbitration algorithm, these BUS masters compete for BUS access and prioritize their requests to access shared resources.