Patent ID: 6937133

Claim:
An arbitration method for selecting the connections to be made by a crossbar switch of a data switching system between a plurality of ingress ports and a plurality of egress ports, the arbitration method comprising: (i) a request step of at least one ingress port transmitting one or more connection requests indicating egress ports to which a connection is required, (ii) a grant step of examining the connection requests, and, for each egress port for which there is a connection request, selecting one request for grant, and generating a grant signal indicative of the selected request; (iii) an accept step of examining the grant signals and, for each ingress port for which there is a grant signal, selecting one grant signal to accept, thereby defining an ingress to egress port connection across the crossbar switch; (iv) employing, for each possible combination of an ingress port and an egress port, a respective weight value, a connection request only being selected in said grant step if the corresponding weight value is not zero; (v) each time a connection is made in the crossbar switch involving an ingress port and an egress port, decrementing the corresponding weight value; and (vi) in said grant step, if for a given egress port, there are no connection requests having non-zero weight values, resetting the weight values to default values before said selection.