Abstract: In described embodiments, a communication system employing, for example, clock and data recovery (CDR) detects and applies correction for DC offset in an input data stream signal, termed as “DC offset calibration”. DC offset calibration applies static calibration for DC offset in input circuits, such as an input amplifier and detection latches, without input data, and applies statistical calibration for DC offset during operation with an input data stream to correct for dynamic shifts in DC level. Such DC offset calibration employs data eye measurements of the input data stream for detection of DC offset, and applies an opposite DC offset to maintain a relatively balanced data eye during live traffic.

Abstract: In described embodiments, a communication system employing, for example, clock and data recovery (CDR) detects and applies correction for DC offset in an input data stream signal, termed as “DC offset calibration”. DC offset calibration applies static calibration for DC offset in input circuits, such as an input amplifier and detection latches, without input data, and applies statistical calibration for DC offset during operation with an input data stream to correct for dynamic shifts in DC level. Such DC offset calibration employs data eye measurements of the input data stream for detection of DC offset, and applies an opposite DC offset to maintain a relatively balanced data eye during live traffic.

Abstract: The present invention is used to automatically calibrate a SERDES device by utilizing information provided in the eye diagram of the received signal. In particular, the invention mitigates the components of determininistic jitter, such as ISI and frequency distortion. To achieve this goal, the invention enables the receive side of the SERDES to evaluate the quality of the eye received using a cost function. The invention calculates the cost function associated with the received data and then uses this information to effect an auto calibration of the SERDES device.

Abstract: Methods and apparatus are provided for improving the performance of second order CDR systems. The integral state of the CDR system is initialized to a value that is based on an expected frequency profile that may be known a priori for certain applications. One or more quality of lock (QOL) metrics are also monitored that are derived from the integral register state value. A quality of a locking between a received signal and a local clock generated by a Clock and Data Recovery (CDR) system is evaluated by monitoring a state value of an integral register in a digital loop filter of the CDR system; evaluating one or more predefined criteria based on the integral register state value; and identifying a poor lock condition if the one or more predefined criteria are not satisfied.

Abstract: Methods and apparatus are provided for determining a position of an offset latch employed for decision-feedback equalization. The position of an offset latch is determined by obtaining a plurality of samples of a data eye associated with a signal, the data eye comprised of a plurality of trajectories for transitions out of a given binary state; determining an amplitude of at least two of the trajectories based on the samples; and determining a position of an offset latch based on the determined amplitudes. The initial position of the offset latch can be placed, for example, approximately in the middle of the determined amplitudes for at least two of the trajectories. The initial position of the offset latch can be optionally skewed by a predefined amount to improve the noise margin.

Abstract: Methods and apparatus are provided for obtaining a phase offset estimate from a data stream. A binary sampled version of the data stream is obtained based on a clock. A first dot product of the binary sampled version of the data stream and an ideal sequence and a second dot product of the binary sampled version of the data stream and a delayed ideal sequence are accumulated. A phase offset of the clock is adjusted until the accumulated first and second dot product satisfy one or more predefined conditions. For example, the predefined conditions can comprise a transition of at least one of the accumulated first and second dot product or whether at least one of the accumulated first and second dot product transition to a final value.

Abstract: A conventional serial communications protocol that is limited to supporting only host-to-slave communications, such as SATA or SAS, is extended to support peer-to-peer communications, e.g., by adding a memory-map layer into the conventional protocol stack between the link layer and the protocol layer. The addition of the memory-map layer enables two (or more) non-host devices (i.e., peer devices) to communicate with one another without using a host computer and without relying on conventional protocol-bridging techniques.

Abstract: Disclosed is a system and method for a clock and data recovery (CDR) circuit. A phase selection circuit (PSC) generates a signal comprising frequency and phase. A voltage controlled oscillator (VCO) connected to the PSC generates a clock signal. The clock signal controls the frequency of the signal. The CDR circuit also includes a phase adjustment signal generator connected to the PSC for generating a phase adjustment signal. The phase adjustment signal controls the phase of the signal.

Abstract: Methods and apparatus are provided for generating one or more clock signals for a decision-feedback equalizer using DFE detected data. A received signal is sampled using a data clock and a transition clock to generate a data sample signal and a transition sample signal, respectively. A DFE correction is obtained for each of the data sample and transition sample signals to generate DFE detected data and a DFE transition data. The DFE detected data and DFE transition data are then applied to a phase detector that generates a signal to adjust a phase of one or more of the data clock and transition clock. In a multi-level implementation, the received signal is sampled using a clock associated with each of the levels and the samples are latched using a vertical slicing technique to generate DFE data associated with each of said levels.

Abstract: A circuit for spread spectrum rate control uses a first interpolator to phase interpolate between a first signal and a second signal and generate a first output signal based on a first control signal. A second interpolator is utilized to phase interpolate between a third signal and a fourth signal and generate a second output signal based on a second control signal. A multiplexer is used to select, based on a select signal, the first output signal or the second output signal as a spread spectrum clock (SSCLK). A leap-frog interpolator control is used to generate, in synchronism with the SSCLK, the first control signal based on a first type of phase adjustment request, the second control signal based on a second type of phase adjustment request, and the select signal to switch the multiplexer between the first output signal and the second output signal after allowing for an interpolator settling time when changing the first control signal or the second control signal.

Abstract: Methods and apparatus are provided for adjusting receiver gain based on received signal envelope detection. The gain of a received signal is adjusted by obtaining a plurality of samples of the received signal for a given unit interval; determining an amplitude of the received signal based on the samples; and adjusting a receiver gain based on the determined amplitude. The received signal can be sampled, for example, using a plurality of latches. The value of the received signal can then be estimated by evaluating one or more of the latch values. Once the amplitude of the received signal is determined, one or more latches can be positioned at a desired target amplitude and the receiver gain can be adjusted until the amplitude of the received signal is within a desired tolerance of the specified target value.

Abstract: Methods and apparatus are provided for delay line control using receive data. A delay in a Delay-Locked-Loop circuit is controlled by obtaining a plurality of samples of one or more received signals for each unit interval; determining a data eye width in the one or more received signals; and adjusting a delay of at least one clock signal based on the data eye width. For example, the measured data eye width can be compared to a predefined value, such as a desired or ideal value. Generally, the delay is not adjusted in accordance with the present invention until the Delay-Locked-Loop circuit has reached a locked condition based on one or more predefined criteria.

Abstract: Methods and apparatus are provided for monitoring and compensating for skew on a high speed parallel bus. Delay skew for a plurality of signals on a parallel bus is monitored by obtaining a plurality of samples of the plurality of signals for each unit interval; and identifying a location of transitions in the plurality of signals based on the samples. The samples can be obtained, for example, by sampling the plurality of signals using a plurality of latches and estimating a value of one or more of the plurality of signals by comparing values of the latches. A microprocessor can optionally be employed to determine a relative distribution of transitions in the plurality of signals and to align transitions in the plurality of signals to a common position. The transitions in the plurality of signals can be aligned to a common position by adjusting a delay control setting for a buffer associated with each of the plurality of signals.

Abstract: The present invention addresses the generation of a controlled clock source for use in trimming VCDL delay line output clocks. In this trimming process, adjustments are made for static variations in these output clocks. The invention's use of a controlled clock source eliminates the need for this trimming process to be conducted in real time and reduces the expense of the circuitry required.

Abstract: A current mode logic digital circuit is provided comprising a logic circuit component having at least one data input node and at least one output node. A load is coupled between a power supply node and the output node. The load comprises a folded active inductor coupled to the output node.

Abstract: An amplifier having DC offset compensation includes at least one input node and a pair of differential output nodes, a biasing circuit coupled to the input node; and a plurality of current sources.

Abstract: Methods and apparatus are provided for monitoring a data eye associated with a received signal. A plurality of samples of the received signal are obtained for each unit interval based on a clock recovered from the received signal, to obtain an estimate of the data eye. According to one aspect of the invention, the samples are obtained substantially simultaneous to a decoding of the received signal. The collected data eye samples can optionally be processed, for example, to collect statistics on the received signal or to determine a distribution of the received signal.

Abstract: Methods and apparatus are provided for digital linearization of an analog phase interpolator. Up to 2N desired phase values are mapped to a corresponding M bit value, where M is greater than N. A corresponding M bit value is applied to the phase interpolator to obtain a desired one of the 2N desired phase values. A linearized phase interpolator is also provided that accounts for process, voltage, temperature or aging (PVTA) variations.

Abstract: An integrated circuit device for use in a node of a communication system is provided. The integrated circuit device includes a memory configured to store data written thereto by a receiver associated with the node in accordance with a receiver clock, and to read data therefrom by a transmitter associated with the node in accordance with a transmitter clock. The integrated circuit device also includes a control logic circuit that is in communication with the memory, and is configured to send a control signal to the transmitter to adjust a speed of the transmitter clock responsive to an operating condition of the memory.

Abstract: The present invention is used to automatically calibrate a SERDES device by utilizing information provided in the eye diagram of the received signal. In particular, the invention mitigates the components of determininistic jitter, such as ISI and frequency distortion. To achieve this goal, the invention enables the receive side of the SERDES to evaluate the quality of the eye received using a cost function. The invention calculates the cost function associated with the received data and then uses this information to effect an auto calibration of the SERDES device.