The missing pulse monitor uses a window detector to validate input clock pulses that arrive within the nominal clock period plus a programmable late window threshold (T_LATE). When an input pulse arrives before T_LATE, the pulse is considered valid and the missing pulse flag will be cleared if set. When an input pulse does not arrive before T_LATE (due to a missing or late pulse), the missing pulse flag is set to disqualify the input.

Typically, T_LATE should be set higher than the input's longest clock period (including cycle-to-cycle jitter), or higher than the gap width for a gapped clock. The missing pulse monitor can act as a coarse frequency detector with faster detection than the ppm frequency detector. The missing pulse monitor is supported for input frequencies between 2 kHz and f_VCO/12 and should be disabled when outside this range.

The missing pulse and runt pulse monitors operate from the same window detector block for each reference input. The status flags for both these monitors are combined by logic-OR gate and can be observed through status pin. The window detector flag for a reference can also be observed through the corresponding REFx_MISSCLK_STATUS bit.