In one embodiment of the invention, a phase selection unit for generating a recovered clock signal (SCLK), a phase select signal generator generates a phase select signals in response to a FWD signal and a BWD signal from a digital filter. The digital filter asserts the FWD signal if the phase of a SDIN (serial digital input) signal leads the phase of the recovered clock signal, and asserts the BWD signal if the phase of the SDIN (serial digital input) signal lags the phase of the recovered clock signal. A multiplexer receives a number of given clock signals arranged in a predetermined phase order and outputs selected first and second output clock signals, each being one of the given clock signals. A phase interpolator receives the selected first and second output clock signals from the multiplexer to generate the recovered clock signal having a phase that is phase interpolated between the phases of the first and second output clock signals.
An efficient filter circuit and method for filtering a loss of receiver signal prevents false signals caused by glitches. The short glitches that happen at the positive edge of the clock signal may be prevented from affecting the whole clock cycle. The false signal removal circuitry is effective against both false active high and false active low signals. A selectable majority determination block also measures the number of glitches or average signal strength to determine that a valid signal is present. A mininum pulse width of a glitch is settable.
A system and method for tracking/adapting phase or frequency changes in an incoming serial data stream that may contain significant amounts of noise and/or jitter and may contain relatively long periods of successive univalue data bits. The method includes digitally sampling a received data stream at predefined intervals to produce a data set; estimating when logic transitions occur in the data set; detecting a timing trend represented by the estimated logic transitions; and adjusting a frequency of the first clock so that the timing trend averages approximately zero over a plurality of logic transitions.
Core clock alignment circuits include a serial-in parallel-out (SIPO) data processing circuit, which is configured to generate a plurality of lanes of deserialized data in response to a corresponding plurality of lanes of serialized data. The SIPO data processing circuit is further configured to generate a plurality of recovered clock signals from corresponding ones of the plurality of lanes of serialized data. These recovered clock signals may be out-of-phase relative to each other. The devices also include a plurality of lane FIFOs, which are configured to receive respective ones of the plurality of lanes of deserialized data and respective ones of the plurality of recovered clock signals at write ports thereof. A core clock alignment circuit is provided, which may be electrically coupled to the plurality of lane FIFOs. The core clock alignment circuit is configured to perform clock phase learning operations to generate a core clock in response to detecting a plurality of training state headers received by the plurality of lane FIFOs. This core clock may be provided to read ports of the plurality of lane FIFOs to thereby synchronize FIFO read operations.
