Data processing apparatus and method for performing multi-cycle arbitration

Abstract

A data processing apparatus and method are provided for arbitrating between multiple access requests seeking to access a plurality of resources sharing a common access path. At least one logic element issues access requests requesting access to the resources, and each access request identifies which of the resources is to be accessed. Arbitration circuitry performs a multi-cycle arbitration operation to arbitrate between multiple access requests to be passed over the common access path, the arbitration circuitry having a plurality of pipeline stages to allow a corresponding plurality of multi-cycle arbitration operations to be in progress at any one time. Filter circuitry is provided which has a plurality of filter states, the number of filter states being dependent on the number of pipeline stages of the arbitration circuitry, and each resource being associated with one of the filter states. For a new multi-cycle arbitration operation to be performed by the arbitration circuitry, the filter circuitry selects one of the filter states that has not been selected for any other multi-cycle arbitration operation already in progress within the pipeline states of the arbitration circuitry. Then, it determines as candidate access requests for the new multi-cycle arbitration operation those access requests that are seeking to access a resource associated with the selected filter state. Such an approach allows efficient multi-cycle arbitration to take place even where the resources may have inter-access timing parameters associated therewith which prevent them from being able to receive access requests every clock cycle.