Asynchronous processor access to a switch table in a network with isochronous capability

Apparatus for communicating between at least first and second stations in a data communication system over at least a first link, said data communication system including a plurality of data sources and sinks, at least a first of said sources and sinks configured to receive or transmit data isochronously and a second of said sources and sinks configured to transmit data non-isochronously, the apparatus comprising:

• at least a first receiver and at least a first transmitter in said first station;
• said first link coupling said first station with said second station;
• said second station being coupled to both said first and second of said sources and sinks;
• a second transmitter in said second station for transmitting data to said first receiver;
• a first multiplexer in said second station for permitting the transmitting of data from both of said first and second sources and sinks over said first link as first multiplexed data, said multiplexer providing a first, dedicated bandwidth for first data originating from an isochronous source, including at least said first of said sources and sinks;
• at least a first updatable switchtable in said first station for storing information indicating at least the destination of data;
• a microprocessor operating according to a first clock, coupled to said updatable switchtable, said updatable switchtable operating according to a second clock asynchronously with said first clock;
• a register coupled to said microprocessor for receiving update data from said microprocessor during a first time period at a data rate corresponding to said first clock and coupled to said first updatable switchtable for outputting said update data to said first updatable switchtable.

A method for communicating data over a data link in a data communication system between a first station coupled to a first endpoint of said data link and a second station coupled to a second endpoint of said data link, said second station having both an isochronous data source and a non-isochronous data source, said data communication system having a time-varying amount of non-isochronous demand, the method comprising;

• time-division multiplexing data from said isochronous data source and said non-isochronous data source according to a periodically repeating frame structure, said frame structure defining at least a first dedicated bandwidth for data from said isochronous source, wherein the data transfer rate for said isochronous data is substantially independent of the non-isochronous demand on said data system;
• providing a microprocessor in said first station operating according to a first clock and an updatable table operating according to a second clock asynchronously with said first clock;
• receiving update data in a holding register from said microprocessor during a first time period at a data rate corresponding to said first clock, said update data including at least destination data;
• updating said updatable table asynchronously with said first clock, using at least some of said update data in said holding register;
• and
• transmitting the time-multiplexed data onto said data link in accordance with data stored in said updatable table.