US Patent 7254797 Input/output cells with localized clock routing

Described are approaches to routing buffered reference clock signals to a plurality of input/output (I/O) cell instances on an integrated circuit (IC) die. All or a subset of the I/O cell instances include clock routing resources optimized to deliver high-speed, low jitter clock signals within and through the particular instance. The clock routing resources in physically adjacent instances of the input/output cells for a given IC die automatically interconnect, collectively forming clock routing infrastructure optimized for groups of cell instances. This modular approach to clock routing simplifies the task of combining I/O cell instances with other I/O cell instances and with other types of circuitry.