System having a spread-spectrum clock for further suppression of electromagnetic emissions in network devices communicating via a network bus

A network system comprising:

• a network comprising:
• a network bus electrically connected to a plurality of remote devices;
• and
• a network controller for digitally directing transmissions with the plurality of remote devices via said network bus;
• and
• a plurality of network device interface elements adapted to interconnect said network controller with respective remote devices via said network bus, each network device interface element comprising:
• a local oscillator capable of issuing clock signals having at least one frequency for controlling a rate at which said network device interface element transmits and receives messages;
• and
• a spread-spectrum clock for receiving the clock signals issued by said local oscillator and for spreading energy of the clock signals over a plurality of frequencies wider than the at least one frequency of the local oscillator so as to at least partially limit electromagnetic emissions from said local oscillator,
• wherein each network device interface element is capable of transmitting and receiving messages via said network bus, wherein said network device interface element is capable of determining if clock signals are provided with messages received via said network bus such that said network device interface is capable of transmitting messages in one of a synchronous mode and an asynchronous mode based upon the determination.

A network device interface element adapted to interconnect a network controller with an associated remote device via a network bus, the network device interface element comprising:

• a transceiver capable of transmitting and receiving messages via the network bus;
• a processing element for providing commands to the associated remote device in response to messages received by said transceiver and for receiving data from the associated remote device, wherein said network device interface element is capable of determining if clock signals are provided with messages received by said transceiver such that the network device interface is capable of transmitting messages in one of a synchronous mode and an asynchronous mode based upon the determination;
• a local oscillator capable of issuing clock signals having at least one frequency for controlling a rate at which said network device interface element transmits and receives messages;
• and
• a spread-spectrum clock for receiving the clock signals issued by said local oscillator and for spreading energy of the clock signals over a band of frequencies, centered around or for a band spaced above or for a band spaced below the at least one frequency of the local oscillator so as to at least partially limit electromagnetic emissions from said local oscillator, wherein said spread-spectrum clock drives said transceiver and said processing element.

A network device interface element adapted to interconnect a network controller with an associated remote device via a network bus, the network device interface element comprising:

• a transceiver capable of transmitting and receiving messages via the network bus;
• a processing element for providing commands to the associated remote device in response to messages received by said transceiver and for receiving data from the associated remote device, wherein said network device interface element is capable of determining if clock signals are provided with messages received by said transceiver such that the network device interface is capable of transmitting messages in one of a synchronous mode and an asynchronous mode based upon the determination;
• a local oscillator capable of issuing clock signals having at least one frequency for controlling a rate at which said network device interface element transmits and receives messages;
• a spread-spectrum clock for receiving the clock signals issued by said local oscillator and for spreading energy of the clock signals over a plurality of frequencies wider than the at least one frequency of the local oscillator so as to at least partially limit electromagnetic emissions from said local oscillator, wherein said spread-spectrum clock drives said transceiver and said processing element;
• and
• a suppression assembly adapted to at least partially limit electromagnetic emissions from said transceiver and said processing element, said suppression assembly comprising:
• an isolation transformer;
• a common mode choke electrically connected to the network bus between said isolation transformer and the network bus;
• and
• a low pass filter electrically connected between said transceiver and said isolation transformer.