Method and apparatus for synchronizing data received in an accelerated graphics port of a graphics memory system

DETAILED DESCRIPTION The present invention provides a method and apparatus for receiving and synchronizing data transmitted to a host interface unit of a graphics memory system on the rising and falling edges of a strobe signal in accordance with an accelerated graphics port (AGP) specification.
The apparatus of the present invention comprises an inner loop synchronization component which is comprised in the host interface unit of the graphics memory system.
The inner loop synchronization component receives data transmitted to the inner loop synchronization component on the falling and rising edges of a strobe signal and synchronizes the data to a PCI clock signal.
The inner loop synchronization component comprises a first data transfer unit, a second data transfer unit and a control unit.
The first data transfer unit comprises logic configured to capture the data transmitted on the falling edge of the strobe signal and to delay the captured data a predetermined number of cycles of the PCI clock before outputting the captured data from the first data transfer unit.
The control unit detects the falling edge of the strobe signal and generates a timing signal that is derived from the strobe signal.
The second data transfer unit comprises logic configured to capture the data transmitted on the rising edge of the strobe signal.
The second data transfer unit receives the timing signal generated by the control unit and utilizes the timing signal to capture the data transmitted on the rising edge of the strobe signal.
The second data transfer unit comprises logic configured to capture the data transmitted on the rising edge of the strobe signal and to delay the captured data a predetermined number of cycles of the clock before outputting the captured data from the second data transfer unit.
The rising edge of the strobe signal may or may not occur within the PCI clock cycle in which the falling edge of the strobe signal occurs.
The second data transfer unit comprises logic for detecting the rising edge of the strobe signal and capturing the data transmitted on the rising edge