Abstract: A method and circuit for measuring a time interval between transitions of periodic signals at nodes of a circuit-under-test (CUT), the signals having a periodic clock frequency, the method includes periodically latching a digital value of a first periodic signal at edges of an undersampling clock, simultaneously periodically latching a digital value of a second periodic signal at edges of the undersampling clock, combining the latched digital values of the first and second periodic signals to produce a combined output whose duty cycle is proportional to the time interval between a median edge of latched digital values of the first periodic signal and a median edge of latched digital values of the second periodic signal; and counting the number of undersampling clock cycles in which the combined output is a predetermined logic value within a predetermined time interval whereat the number is proportional to a time interval between a transition of the first periodic signal and a transition of the second periodic

Abstract: A method and circuit for measuring a statistical value of jitter for a data signal having a data rate fD, comprises digitally sampling the data signal at a sampling rate, fS, to produce sampled logic values, where fD/fS is a predetermined non-integer ratio; and analyzing the sampled values to deduce a statistical value of the jitter.

Abstract: A circuit and method are described in which a DC voltage or current is connected to a high frequency, AC-coupled signal path between a transmitter and a receiver, and the bit error rate of the data transmission is tested while applying an altered bias voltage to the received signal. The bias voltage can be connected via a resistor, inductor or transistors. The transmitted signal is attenuated resistively, and a load capacitance is applied whose value causes digital transition times to exceed one unit interval. An intended application is testing of an integrated circuit, serializer/deserializer (serdes) operating above 1 GHz.

Abstract: A circuit and method are described in which a DC voltage or current is connected to a high frequency, AC-coupled signal path between a transmitter and a receiver, and the bit error rate of the data transmission is tested while applying an altered bias voltage to the received signal. The bias voltage can be connected via a resistor, inductor or transistors. The transmitted signal is attenuated resistively, and a load capacitance is applied whose value causes digital transition times to exceed one unit interval. An intended application is testing of an integrated circuit, serializer/deserializer (serdes) operating above 1 GHz.

Abstract: A method of synthesizing a circuit employs a technology parameter extraction circuit which is synthesized with constraints and simulated to derive values of performance parameters, and then, based on the derived values, a predetermined high-level circuit description of a second circuit is modified and then synthesized using the same constraints. Optional steps include the creation and substitution of a sub-circuit model to permit correct simulation, or substitution of an alternative sub-circuit to synthesize a second circuit that cannot otherwise be synthesized directly.

Abstract: A method of testing phase locked loops (PLL) and a testing circuit comprising the steps of applying a normal stimulus signal whose frequency is within the lock range of the PLL to the input of the PLL, substituting the normal input stimulus with an alternative signal derived from an internal feedback of the PLL, adding or deleting one or more cycles from the alternative signal and observing the response of the PLL to the alternative signal. Variations of the method allow for determining Gain-Bandwidth product, lock range, lock time, Bit Error Rate, Jitter and other parameters which can then be compared with predetermined values to determine whether the PLL is properly functional.

Abstract: A circuit and method is described which generates a high frequency clock signal whose frequency is accurate enough to be used for testing other circuitry, yet the circuit can be described using a hardware description language so that it is suitable for logic synthesis and automatic layout. The technique uses a plurality of programmable ring oscillators and means to select and enable one of the ring oscillators. The output frequency is measured relative to that of a lower frequency reference signal, and when the output frequency is incorrect, a different ring oscillator is selected or the present ring oscillator's frequency is changed. Circuitry is included to prevent glitches at the output of the clock generator when the frequency is changed, regardless of how the ring oscillators are constructed.