Synchronous bridge circuitry and a method of transferring data using asynchronous bridge circuitry

Asynchronous bridge circuitry for transferring data from source circuitry operating in a source clock domain to destination circuitry operating in a destination clock domain that is asynchronous with respect to said source clock domain, said asynchronous bridge circuitry comprising:

• first-in-first-out buffer means for storing data values, said first-in-first-out buffer means being located within said source clock domain and comprising a buffer output for coupling to said destination circuitry in said destination clock domain and a plurality buffer register means for storing said data values;
• transmission path means for transmitting said data from said source circuitry to said first-in-first-out buffer means with a transmission delay corresponding to one or more source clock signals, said transmission path means having an input end for coupling to said source circuitry and an output end coupled to said first-in-first-out buffer means;
• write pointer means for generating a write pointer coupled to said first-in-first-out buffer means to select a current write location within said first-in-first-out buffer means and corresponding to one of said plurality of buffer registers means, said write pointer means being located within said source clock domain at said output end of said transmission path means;
• and
• transmission control means for generate a transmission control signal for controlling whether or not said source circuitry is permitted to send said data to said first-in-first-out buffer means, said transmission control means being located within said source clock domain at said input end of said transmission path means, wherein
• said transmission control means comprises tracking means for storing one or more tracking values for tracking respective state variables of said first-in-first-out buffer means, said transmission control means generating said transmission control signal in dependence upon said one or more tracking values.

A method of transferring data, using asynchronous bridge circuitry, from source circuitry operating in a source clock domain to destination circuitry operating in a destination clock domain that is asynchronous with respect to said source clock domain, said method comprising the steps of:

• storing data values within a first-in-first-out buffer, said first-in-first-out buffer being located within said source clock domain and comprising a buffer output for coupling to said destination circuitry in said destination clock domain and a plurality buffer registers for storing said data values;
• transmitting said data from said source circuitry to said first-in-first-out buffer along a transmission path with a transmission delay corresponding to one or more source clock signals, said transmission path having an input end coupled to said source circuitry and an output end coupled to said first-in-first-out buffer;
• generating with write pointer circuitry a write pointer coupled to said first-in-first-out buffer to select a current write location within said first-in-first-out buffer and corresponding to one of said plurality of buffer registers, said write pointer circuitry being located within said source clock domain at said output end of said transmission path means;
• generating with transmission control circuitry a transmission control signal for controlling whether or not said source circuitry is permitted to send said data to said first-in-first-out buffer, said transmission control circuitry being located within said source clock domain at said input end of said transmission path circuitry;
• and
• storing within said transmission control circuitry one or more tracking values for tracking respective state variables of said first-in-first-out buffer, wherein
• said step of generating said transmission control signal is dependent upon said one or more tracking values.