Arbitration system

A bus arbitration system is described which includes an arbiter for controlling accesses to a memory bus by a plurality of memory users in response to requests made by those memory users. Each memory user reads the address if a current access to memory and generates a same-address-set signal when the address of the last access by that memory user lies in the same set as the address of the current access. The arbiter holds for each memory user a predetermined number of accesses which are permitted by that memory user during an access span, and, responsive to a request, grants up to that predetermined number of accesses provided that the same-address-set signal is asserted.