Viavi Solutions Inc.
DIGITAL CIRCUIT TO DETECT PRESENCE AND QUALITY OF AN EXTERNAL TIMING DEVICE

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.