Method of detecting a source strobe event using change detection

A method of detecting a source strobe event in a processor based system, the system comprising a hub device coupled to a processor by a processor bus and coupled to a memory device by a memory bus, the hub device being connected to a satellite device by a link bus, the link bus comprising at least one source strobe signal line associated with a first clock domain, said method comprising the steps of:

• inputting at one of the hub device and the satellite device information associated with the source strobe event from the link bus, the information being input into first circuitry associated with the first clock domain;
• sampling the input information from the first circuitry into second circuitry associated with a second clock domain;
• determining from the sampled information whether the second circuitry is in a known state;
• and
• processing the source strobe event if it is determined that the second circuitry is not in the known state.

A receiving circuit for detecting and receiving a source strobe event from a source strobed bus, said circuit comprising:

• a first data circuit for inputting information associated with the source strobe event from the bus, said first data circuit having a first output and being clocked by a source strobe signal associated with the bus;
• a second data circuit connected to said first output, said second data circuit having a second output and being clocked by a second clock signal associated with a clock of said receiving circuit, said second data circuit continuously sampling said first output and outputting said second output responsive to said second clock signal;
• and
• a change detect circuit connected to receive said second output, said change detect circuit determining whether said second data circuit is in a known state and processing the source strobe event if it is determines that said second data circuit is not in the known state.

A receiving circuit for detecting and receiving a source strobe event from a source strobed bus, said circuit comprising:

• a source strobe macro connected to the source strobe bus, said source strobe macro receiving source strobes from the bus, generating a plurality of additional strobes based on the received strobes and outputting said additional strobes;
• a plurality of data macros connected to the source strobe bus and to the additional strobes, each of said plurality of data macros inputting information associated with the source strobe event from the bus and in response to said additional strobes, sampling the information into a clock domain associated with a core logic clock of said receiving circuit and outputting clock domain information;
• and
• a change detect circuit connected to receive said clock domain information and a control signal, said change detect circuit in response to said control signal determines whether the bus is a known state based on said clock domain information and processes the source strobe event when the bus is not in the known state.

A processor based system comprising:

• a processor;
• a link hub coupled to said processor by a processor bus;
• a satellite device coupled to said link hub by a link bus, said link bus being a source strobed bus, at least one of said satellite device and said link hub including a receiving circuit for detecting and receiving a source strobe event from said link bus, said receiving circuit comprising:
• a first data circuit for inputting information associated with the source strobe event from said bus, said first data circuit having a first output and being clocked by a source strobe signal associated with said bus;
• a second data circuit connected to said first output, said second data circuit having a second output and being clocked by a second clock signal associated with a clock of said receiving circuit, said second data circuit continuously sampling said first output and outputting said second output responsive to said second clock signal;
• and
• a change detect circuit connected to receive said second output, said change detect circuit determining whether said second data circuit is in a known state and processing the source strobe event if it is determines that said second data circuit is not in the known state.

A processor based system comprising:

• a processor;
• a link hub coupled to said processor by a processor bus;
• a satellite device coupled to said link hub by a link bus, said link bus being a source strobed bus, at least one of said satellite device and said link hub including a receiving circuit for detecting and receiving a source strobe event from said link bus, said receiving circuit comprising:
• a source strobe macro connected to said link bus, said source strobe macro receiving source strobes from said bus, generating a plurality of additional strobes based on the received strobes and outputting said additional strobes;
• a plurality of data macros connected to said link bus and to the additional strobes, each of said plurality of data macros inputting information associated with the source strobe event from said bus and in response to said additional strobes, sampling the information into a clock domain associated with a core logic clock of said receiving circuit and outputting clock domain information;
• and
• a change detect circuit connected to receive said clock domain information and a control signal, said change detect circuit in response to said control signal determines whether said bus is a known state based on said clock domain information and processes the source strobe event when said bus is not in the known state.