An integrated circuit includes a plurality of receivers, each having a clock and data recovery circuit. A first local clock recovery circuit in a first receiver can be caused to produce a test clock which simulates a condition to be tested, and while a second receiver in the plurality of receivers that includes a second local clock recovery circuit is caused to use the test clock in place of the reference clock while receiving a test data sequence at its input. The clock and data recovery circuits in the receivers can include clock control loops responsive to loop control signals to modify the selected reference clock to generate the local clock in response to selective one of (i) a corresponding data signal for normal operation or during a test, and (ii) a test signal applied to the clock control loop in which case the test clock is produced.

A circuit for measuring latency in an integrated circuit device is described. The circuit comprises a transmitter circuit having signal generator configured to generate a test signal having a marker for determining a latency in a path associated with the integrated circuit device; and a latency calculation circuit coupled to the signal generator and having a latency adjustment circuit and a unit interval (UI) adjustment circuit; wherein the latency calculation circuit generates a latency value (LATENCY) based upon a latency count from the latency adjustment circuit and a UI adjustment from the UI adjustment circuit.

Various aspects describe an on-chip, hardware error-generator component. In some cases, the hardware error-generator component connects to a data path between two components contained within a same chip. Upon receiving an error simulation input, the hardware error-generator component modifies data being transmitted on the data path by inserting a data pattern that simulates an error condition. Alternately or additionally, the hardware error-generator randomly alters one or more of the transmitted data bits.

An integrated circuit includes a plurality of receivers, each having a clock and data recovery circuit. A first local clock recovery circuit in a first receiver can be caused to produce a test clock which simulates a condition to be tested, and while a second receiver in the plurality of receivers that includes a second local clock recovery circuit is caused to use the test clock in place of the reference clock while receiving a test data sequence at its input. The clock and data recovery circuits in the receivers can include clock control loops responsive to loop control signals to modify the selected reference clock to generate the local clock in response to selective one of (i) a corresponding data signal for normal operation or during a test, and (ii) a test signal applied to the clock control loop in which case the test clock is produced.

An integrated circuit includes a plurality of receivers, each having a clock and data recovery circuit. A first local clock recovery circuit in a first receiver can be caused to produce a test clock which simulates a condition to be tested, and while a second receiver in the plurality of receivers that includes a second local clock recovery circuit is caused to use the test clock in place of the reference clock while receiving a test data sequence at its input. The clock and data recovery circuits in the receivers can include clock control loops responsive to loop control signals to modify the selected reference clock to generate the local clock in response to selective one of (i) a corresponding data signal for normal operation or during a test, and (ii) a test signal applied to the clock control loop in which case the test clock is produced.

A redriver is provided that includes a receiver to receive a signal from a first device that includes a portion of a defined binary sequence, a drift buffer to retime the binary sequence and provide a seed to a linear feedback shift register (LFSR) from the binary sequence, the LFSR to generate an expected version of the binary sequence from the seed, and pattern checking logic to compare a sequence in subsequent signals received from the first device with the expected version of the binary sequence generated by the LFSR.

Described are methods and circuits for margin testing digital receivers. These methods and circuits prevent margins from collapsing in response to erroneously received data, and can thus be used in receivers that employ historical data to reduce intersymbol interference (ISI). Some embodiments detect receive errors for input data streams of unknown patterns, and can thus be used for in-system margin testing. Such systems can be adapted to dynamically alter system parameters during device operation to maintain adequate margins despite fluctuations in the system noise environment due to e.g. temperature and supply-voltage changes. Also described are methods of plotting and interpreting filtered and unfiltered error data generated by the disclosed methods and circuits. Some embodiments filter error data to facilitate pattern-specific margin testing.

A circuit that introduces a calibrated amount of jitter and/or amplitude variation into a signal. By generating a signal with some predetermined amount of variation, signal consuming equipment may be tested to verify that it can properly extract the information from the signal, despite the presence of such variation. The circuit includes a signal propagation channel through which a signal may propagate. However, to introduce signal variation, the signal propagation channel passes close to electromagnetic interference generation circuitry. A calibration circuit has one or multiple settings that sets on or more values of parameters of the electromagnetic interference generation circuitry. During calibration, the parameters are adjusted until desired variation is detected, and which point the calibrated values are set and associated with that signal variation. This may be repeated for multiple calibration values and multiple settings. The ability to handle signals of different variances may then be accomplished.

Various aspects describe an on-chip, hardware error-generator component. In some cases, the hardware error-generator component connects to a data path between two components contained within a same chip. Upon receiving an error simulation input, the hardware error-generator component modifies data being transmitted on the data path by inserting a data pattern that simulates an error condition. Alternately or additionally, the hardware error-generator randomly alters one or more of the transmitted data bits.

A circuit that introduces a calibrated amount of jitter and/or amplitude variation into a signal. By generating a signal with some predetermined amount of variation, signal consuming equipment may be tested to verify that it can properly extract the information from the signal, despite the presence of such variation. The circuit includes a signal propagation channel through which a signal may propagate. However, to introduce signal variation, the signal propagation channel passes close to electromagnetic interference generation circuitry. A calibration circuit has one or multiple settings that sets on or more values of parameters of the electromagnetic interference generation circuitry. During calibration, the parameters are adjusted until desired variation is detected, and which point the calibrated values are set and associated with that signal variation. This may be repeated for multiple calibration values and multiple settings. The ability to handle signals of different variances may then be accomplished.