Frequency Ratio Detection

A system and method are provided for determining a frequency ratio in a phase-locked loop (PLL) circuit feedback path. The method accepts a reference signal having a predetermined first frequency and a PLL output signal having a non-predetermined second frequency. The reference signal cycles are counted, creating a first binary count. Likewise, the PLL output signal cycles are counted, creating a second binary count. The second binary count is sampled at an interval responsive to the first binary count, and a right-shifted second binary count is supplied as a ratio of the second frequency divided by the first frequency. More explicitly, the sampling is performed when a first binary count sampling threshold of 2n first frequency cycles is reached. Then, the radix point in the second binary count is shifted n number of radix places to the left.