Abstract: A management frame circuit has a set of inputs coupleable to a management bus for carrying management frames. Upon receiving the management frames from the management bus, the management frame circuit determines whether each of the management frames conforms to a frame template. The management frame circuit then asserts an indication that a management frame is bad, if the management frame is determined to not conform to the frame template. The bad fame indication is later deasserted in response to recognition of a predetermined set of bits on the management bus.

Abstract: A clock multiplexer including a plurality of clock selection circuits. Each clock selection circuit determines if a clock input is selected and provides the clock input to a clock output based on the determination. Each clock selection circuit further includes deselect inputs, and a select input which is coupled to a deselect output, the deselect output providing a signal indicating if the select input is active. Each deselect input is connected to a respective one of the deselect outputs from the other clock selection circuits. In each clock selection circuit, the clock input is not provided to the clock output when one of the deselect inputs is active.

Abstract: A data communication system, such as a local area network, is provided with a capability of transmitting isochronous data. Preferably the system conveys both isochronous data and non-isochronous data by time-multiplexing the data into a recurring frame structure on a four-bit nibble basis. An efficient encoding scheme permits transmission of both isochronous and non-isochronous data over existing media, such as twisted pair, without degrading bandwidth previously achieved for non-isochronous data over the same media, such as using an ethernet system. Bandwidth available for a particular isochronous source/sink is selectable and sustainable with a predefined granularity. The arriving data is de-multiplexed at the hub into separate channels for handling the separate streams by appropriate hardware. Preferably, the present invention can be implemented in a fashion that is transparent to already-installed media access controllers.

Abstract: The present invention provides for communication of data to and from isochronous data sources and sinks. Preferably, a portion of bandwidth on the link is also dedicated to convey data to and from non-isochronous sources and sinks, as well as to permit conveying housekeeping information (such as information relating to data sources and destinations) and status and control maintenance information. A management port is included in the isochronous switching devices to allow monitoring or diagnostic access to the serial isochronous data stream to and from all physical layer portion connections. Accessing one connection's data stream does not affect normal operation of the other connections.

Abstract: A data communication system, such as a local area network, is provided with a capability of transmitting isochronous data. Preferably the system conveys both isochronous data and non-isochronous data by time-multiplexing the data into a recurring frame structure on a four-bit nibble basis. An efficient encoding scheme permits transmission of both isochronous and non-isochronous data over existing media, such as twisted pair, without degrading bandwidth previously achieved for non-isochronous data over the same media, such as using an ethernet system. Bandwidth available for a particular isochronous source/sink is selectable and sustainable with a predefined granularity. The arriving data is de-multiplexed at the hub into separate channels for handling the separate streams by appropriate hardware. Preferably, the present invention can be implemented in a fashion that is transparent to already-installed media access controllers.