A clock data recovery circuit may include: a phase comparison unit suitable for comparing input data with a phase of a multi-phase clock, and for generating an up/down signal corresponding to the comparison result; a filtering unit suitable for counting the up/down signal based on an upper threshold value and a lower threshold value, for setting, when an overflow occurs, the lower threshold value to an initial value for the count of the up/down signal, or when a underflow occurs, the upper threshold value to the initial value for the count of the up/down signal, and for generating a control code corresponding to one of the underflow and the overflow; and a phase rotating unit suitable for adjusting the phase of the multi-phase clock in response to the control code outputted from the filtering unit.

Embodiments include systems and methods for detecting and correcting phased clock error (PCE) in phased clock circuits (e.g., in context of serializer/deserializer (SERDES) transmission (TX) clock circuits). For example, phased input clock signals can be converted into unit interval (UI) clocks, which can be combined to form an output clock signal. PCE in the output clock signal can be detected by digitally sampling the UI clocks to characterize their respective clock pulse widths, and comparing the respective clock pulse widths (i.e., PCE in the output clock signal can result from pulse width differences in UI clocks). Delay can be applied to one or more UI clock generation paths to shift UI clock pulse transitions, thereby adjusting output clock pulse widths to correct for the detected PCE. Approaches described herein can achieve PCE detection over a wide error range and can achieve error correction with small resolution.

A system and method for performing clock and data recovery. The system sets the phase of a recovered clock signal according to at least three estimates of the frequency offset, or rate of change of the frequency offset, between an arriving signal and the recovered clock signal.

One embodiment of the present invention provides a system for facilitating synchronization of MAC addresses in a fabric switch. During operation, the system divides a number of media access control (MAC) addresses associated with devices coupled to an interface of the switch. The system then computes a checksum for a respective chunk of MAC addresses. In addition, the system broadcasts MAC address information of the chunk to facilitate MAC address synchronization in a fabric switch of which the switch is a member, and to manage the chunks and their corresponding checksum, thereby correcting an unsynchronized or race condition in the fabric switch.

A data reception device that can improve communication quality when transmitting/receiving serial data is to be provided. There is provided the data reception device including a signal generation unit that generates, from serial data received, a first signal whose value is inverted at a rising timing of the serial data and a second signal whose value is inverted at a falling timing of the serial data, and a clock recovery unit that performs clock recovery using the first signal and the second signal generated by the signal generation unit.

A system and method for a frequency detector circuit includes: a transition detector configured to receive a data input and provide a first edge output based on transitions in the data input; a first circuit configured to generate a second edge output; a second circuit configured to generate a third edge output; and a combinational logic configured to output an UP output when at least two of the first edge output, the second edge output, and the third edge output are high and configured to output a DOWN output when the first edge output, the second edge output, and the third edge output are all low.

Described herein are apparatus and methods for highly linear phase rotators with continuous rotation. A method includes generating a first code and a second code based on a desired offset to match a first and second frequency, respectively, calibrating the first code and the second code based on first phase rotator characteristics and second phase rotator characteristics, respectively, generating first N phase offset codes and second N phase offset codes from a calibrated first and second code, respectively, wherein each phase offset code constrains functionality of the first phase rotator and the second phase rotator, respectively, associated with a phase of the input clock to a defined region of operation, rotating a clock using the first N phase offset codes and the second N phase offset codes to match the first and second frequency, respectively.

An electronic device is disclosed. The electronic device comprises a first clock configured to operate at a frequency. First circuitry of the electronic device is configured to synchronize with the first clock. Second circuitry is configured to determine a second clock based on the first clock. The second clock is configured to operate at the frequency of the first clock, and is further configured to operate with a phase shift with respect to the first clock. Third circuitry is configured to synchronize with the second clock.

Systems, devices, and methods related to selecting a sample phase of a signal are disclosed. A method includes sampling a signal including a plurality of symbols with a plurality of different sample phases to obtain sample values of each of the plurality of symbols at each of the plurality of different sample phases. The signal is received from a shared transmission medium. The method also includes determining an edge sample phase of the plurality of different sample phases that corresponds to edges of the symbols based on the sample values. The method further includes determining a center sample phase of the plurality of different sample phases based on the determined edge sample phase, and using the determined center sample phase to determine values of the symbols.

A clock data recovery circuit includes a phase locked loop (PLL), a code signal generator, and a clock and data generator. The PLL generates a plurality of reference clock signals of which frequencies are modulated. Each of the plurality of reference clock signals has a first profile that is periodically fluctuated. The code signal generator generates a first compensation code signal. The first compensation code signal has a second profile that is periodically fluctuated and is different from the first profile. The clock and data generator generates a recovered data signal by sampling an input data signal based on a clock signal, compensates a frequency modulation on the plurality of reference clock signals based on the first compensation code signal, and includes a phase interpolator that generates the clock signal based on the plurality of reference clock signals and the first compensation code signal.