Abstract: A system for determine presence or quality of an external timing device is provided. The system may include a circuit (e.g., in a field-programmable gate array (FPGA)) having an input, an oscillator, an edge detector, a bit counter, and a calculator element. In some examples, the input may receive an input signal under test. The oscillator may advance a timer at a known rate to facilitate generation of clock samples for the input signal under test. The edge detector may measure edges of the input signal under test based on the clock samples. The circuit may include at least one bit counter to store a count associated with the measured edges for a shorter interval timer period and a longer interval timer period. The calculator element may determine presence or quality of an external timing device based on the count.

Abstract: A system for determine presence or quality of an external timing device is provided. The system may include a circuit (e.g., in a field-programmable gate array (FPGA)) having an input, an oscillator, an edge detector, a bit counter, and a calculator element. In some examples, the input may receive an input signal under test. The oscillator may advance a timer at a known rate to facilitate generation of clock samples for the input signal under test. The edge detector may measure edges of the input signal under test based on the clock samples. The circuit may include at least one bit counter to store a count associated with the measured edges for a shorter interval timer period and a longer interval timer period. The calculator element may determine presence or quality of an external timing device based on the count.

Abstract: A clock and data recovery circuit injects a noise waveform into the control loop to offset the data sampling point artificially in order to induce errors. The amplitude of the injected waveform can be varied to ascertain the effect on the bit error rate (BER) so as to be able to evaluate the temporal noise margin.

Abstract: A clock and data recovery circuit injects a noise waveform into the control loop to offset the data sampling point artificially in order to induce errors. The amplitude of the injected waveform can be varied to ascertain the effect on the bit error rate (BER) so as to be able to evaluate the temporal noise margin.