Counting circuit for measuring pulse spacing, sampling circuit, skew adjusting circuit, and logic analyzing circuit

摘要

There is provided a time counting circuit which measures a pulse spacing of a pulse signal with a high accuracy and exhibits high resistance to variations in power-source voltage. A delay circuit ring consists of a plurality of delay circuits connected in a ring configuration and signal transition is caused to circulate around the delay circuit ring by oscillation. A switch-signal generating circuit outputs first and second switch signals based on the time at which a pulse signal to be measured rises. A row of sampling circuits consists of a plurality of sampling circuits connected to the output terminals of the respective delay circuits and samples the output signals from the delay circuits in response to a direction indicated by the first switch signal. A row of holding circuits consists of a plurality of holding circuits connected to the output terminals of the respective sampling circuits and holds the output signals from the sampling circuits in response to a direction indicated by the second switch signal. An operating circuit calculates the pulse spacing of the pulse signal to be measured based on a logic level signal outputted from the row of holding circuits.