Routing arbitration for shared resources

摘要

A data communicating device, having a number of inputs whereat data is received for communication from one of a number of outputs of the device, includes apparatus for providing two levels of arbitration to select one of the inputs for data communication to an output. The first (lower) level of arbitration bases selection upon a round-robin order; the second (higher) arbitration level selects inputs based upon an indication from an input of an undue wait for access to the output over a period of time. Each input is provided a modulo-N counter, and a digital counter. Each time an input contends for access to an output and loses to selection by the output to another input, the modulo-N counter is incremented by an assigned value for that input. When N is exceed without access, the digital counter is incremented. The content of the counter operates to force the high-level arbitration.