A computer system may periodically calibrate an oscillator subsystem, which includes a voltage-controlled oscillator circuit configured to generate an oscillator signal using code signal. In response to activation of a calibration mode, an iterative calibration operation may be performed on the voltage-controlled oscillator circuit. In some cases, performing a given iteration of the calibration operation includes determining a value of the code signal using a number of pulses in the oscillator signal sampled during a particular time period, along with previous values of the code signal and a slope of an error function associated with the difference between a desired frequency and a current frequency of the oscillator signal. In other cases, iterations may employ variable sampling times with error handling, in order to decrease the duration of the calibration operation while maintaining a target accuracy.

A computer system may periodically calibrate an oscillator subsystem, which includes a voltage-controlled oscillator circuit configured to generate an oscillator signal using code signal. In response to activation of a calibration mode, an iterative calibration operation may be performed on the voltage-controlled oscillator circuit. In some cases, performing a given iteration of the calibration operation includes determining a value of the code signal using a number of pulses in the oscillator signal sampled during a particular time period, along with previous values of the code signal and a slope of an error function associated with the difference between a desired frequency and a current frequency of the oscillator signal. In other cases, iterations may employ variable sampling times with error handling, in order to decrease the duration of the calibration operation while maintaining a target accuracy.

A clock and data recovery circuit includes a sampling circuit, a phase detector, a first processing circuit, a second processing circuit and an oscillator circuit. The sampling circuit is configured to sample input data according to an output clock, and generate a sampling result. The phase detector is configured to generate a detection result according to the sampling result. The first processing circuit is configured to process the sampling result to generate a first digital code. The second processing circuit is configured to accumulate a portion of the first digital code to generate a second digital code. A rate of change of a code value of the second digital code is slower than a rate of change of a code value of the first digital code. The oscillator circuit is configured to generate the output clock according to the detection result, the first digital code and the second digital code.

A clock and data recovery circuit includes a sampling circuit, a phase detector, a first processing circuit, a second processing circuit and an oscillator circuit. The sampling circuit is configured to sample input data according to an output clock, and generate a sampling result. The phase detector is configured to generate a detection result according to the sampling result. The first processing circuit is configured to process the sampling result to generate a first digital code. The second processing circuit is configured to accumulate a portion of the first digital code to generate a second digital code. A rate of change of a code value of the second digital code is slower than a rate of change of a code value of the first digital code. The oscillator circuit is configured to generate the output clock according to the detection result, the first digital code and the second digital code.

A phase-locked loop circuit includes a phase frequency detector (PHD) circuit, a digital code generator circuit, a frequency divider and an oscillator circuit. The PFD circuit is configured to detect a difference in phase and frequency between a reference clock and a feedback clock to generate a first control signal and a second control signal. The digital code generator circuit is configured to process the second control signal to generate a digital code. The frequency divider is configured to receive an output clock to generate the feedback clock. The oscillator circuit is configured to generate the output clock according to the first control signal and the digital code. A frequency of the output clock is determined according to a first control parameter and a second control parameter of different types. The first and second control parameters are adjusted in response to the first control signal and the digital code respectively.

A calibration system of a digital phase locked loop (DPLL) includes a calibration circuit and a digitally controlled oscillator (DCO). The calibration circuit is configured to receive an input signal and a feedback signal, and generate a digital signal, based on a frequency of the input signal, a frequency of the feedback signal, and an input bias code. The DCO is configured to receive the input bias code and the digital signal, and generate a bias signal based on the input bias code. The DCO is further configured to generate an analog signal based on the bias signal and the digital signal, and generate the feedback signal such that the frequency of the feedback signal is based on an amplitude of the analog signal.

A system includes a plurality of oscilloscopes, each oscilloscope having an output port and an input port, a cable connecting the output port of an initial oscilloscope of the plurality of oscilloscopes to the input port of a second oscilloscope of the plurality of oscilloscopes, the initial oscilloscope having a processing element to generate a master run clock, the second oscilloscope having a processing element including a phase-locked loop to lock a slave run clock to the master run clock, wherein the processing element of one of the oscilloscopes executes code to cause the processing element to manipulate one of the run clocks to pass trigger information to another of the plurality of oscilloscopes. A method of synchronizing at least two oscilloscopes including a master oscilloscope and at least one slave oscilloscope includes connecting the at least two oscilloscopes together using output ports and input ports of the at least two oscilloscopes and at least one cable; sending a master run clock from the master oscilloscope to at least one slave oscilloscope; synchronizing a run clock of the at least one slave oscilloscope to the master run clock; recognizing a trigger event at a first oscilloscope of the at least two oscilloscopes; altering the run clock at the first oscilloscope to encode a trigger indication; and receiving the altered run clock at a second oscilloscope of the at least two oscilloscopes, wherein the trigger indication causes the second oscilloscope to recognize the trigger event.

A system includes a plurality of oscilloscopes, each oscilloscope having an output port and an input port, a cable connecting the output port of an initial oscilloscope of the plurality of oscilloscopes to the input port of a second oscilloscope of the plurality of oscilloscopes, the initial oscilloscope having a processing element to generate a master run clock, the second oscilloscope having a processing element including a phase-locked loop to lock a slave run clock to the master run clock, wherein the processing element of one of the oscilloscopes executes code to cause the processing element to manipulate one of the run clocks to pass trigger information to another of the plurality of oscilloscopes. A method of synchronizing at least two oscilloscopes including a master oscilloscope and at least one slave oscilloscope includes connecting the at least two oscilloscopes together using output ports and input ports of the at least two oscilloscopes and at least one cable; sending a master run clock from the master oscilloscope to at least one slave oscilloscope; synchronizing a run clock of the at least one slave oscilloscope to the master run clock; recognizing a trigger event at a first oscilloscope of the at least two oscilloscopes; altering the run clock at the first oscilloscope to encode a trigger indication; and receiving the altered run clock at a second oscilloscope of the at least two oscilloscopes, wherein the trigger indication causes the second oscilloscope to recognize the trigger event.

Described herein are apparatus and methods for a successive approximation register (SAR) analog-to-digital (ADC) based phase-locked loop (PLL) with programmable range. A multi-bit digital phase locked loop includes a multi-bit phase frequency detector configured to output a multi-bit error signal based on a reference clock, a feedback clock sampled using the reference clock, and a threshold voltage, a multi-bit digital low pass filter configured to apply a variable gain to the multi-bit error signal, a current steered digital-to-analog converter configured to generate a control current based on a gain applied multi-bit error signal and multi-bit digital phase locked loop control parameters, a controlled oscillator configured to adjust a frequency of the controlled oscillator based on the control current to generate an output clock, the feedback clock being based on the output clock, and a programmable edge time controller configured to adjust a slope of an edge of the feedback clock.

A phase locked device includes a digital controlled oscillator circuit, a clock signal generator circuitry, a time to digital converter circuit, and a logic control circuit. The digital controlled oscillator circuit is configured to generate a first clock signal in response to a plurality of digital codes. The clock signal generator circuitry is configured to generate a plurality of second clock signals according to the first clock signal, and to select a third clock signal and a fourth clock signal from the plurality of second clock signals according to a selection signal, in order to generate an output signal. The time to digital converter circuit is configured to detect a delay difference between the output signal and a reference signal, in order to generate the plurality of digital codes. The logic control circuit is configured to generate the selection signal according to the plurality of digital codes.