What is bus arbitration?

Bus arbitration is the method used to decide which device gets control of a shared bus when two or more devices want it at the same time. Only one device, called the bus master, can drive the bus at any moment.

The arbiter looks at all the requests. It then grants the bus to one device according to a rule such as fixed priority or rotating priority. When the master finishes its transfer, it releases the bus and the arbiter grants it to the next requester. This prevents two devices from sending data together and corrupting it.