Importance

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Abstract

An apparatus for and a method of collapsing multiple ports to a single queue. The invention has applications in switching devices whereby several external ports share the same resource, such as a switching fabric. In order to allocate the resources fairly to all the ports, a scanning method is used to allocate the division of the resources to each of the external ports. A port combiner circuit continuously scans or polls the external ports in a round robin fashion checking for a port ready to input data. An external port in a ready state transfers its frame data to an input queue. The frame data is written to the next available segment in the input queue which is comprised of RAM configured as a circular buffer. After a frame is written, the write pointer is incremented to point to point to the next available segment. The next frame segment read out of the input queue is always the first one written. The queue thus formed received multiple inputs but has a single output. The scanning method is operative to pass input frames to the shared resource, i.e., the switching fabric, in accordance with their arrival order and without regard to the source port the frame came in on.

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First Claim