Pulse period measurement method
View Patent ↗The effect of chattering on the measurement of the pulse period is reduced. The pulse period representing the rise interval of target pulses appearing in a pulse signal PI is measured. The pulse signal PI is sampled in synchronization with a measurement clock CLK. Measurement of a designated inhibition period is started in synchronization with the fall of the signal PI. Measurement of the current pulse period is completed and measurement of a new pulse period is started if the inhibition period has elapsed at the rise of the signal PI. Counting of the current pulse period is continued if the inhibition period has not elapsed.
1. A pulse period measurement method for measuring a pulse period on the basis of a pulse end in transition from a first state to a second state relative to a target pulse appearing in an input signal, comprising:
a state detection step for sampling the input signal and detecting the signal state at a designated sampling period;
a inhibition period clocking step for starting the process of clocking a designated inhibition period at a first change in which the signal state changes from the second state to the first state; and
a period measurement step for completing the process of measuring the current pulse period and starting the process of measuring a new pulse period if the inhibition period has elapsed by the time of a second change in which the signal state changes from the first state to the second state, and continuing the process of counting the current pulse period if the inhibition period has not elapsed.
2. The pulse period measurement method of claim 1 , wherein
the state detection step detects the signal state in synchronization with a reference clock signal having the sampling period;
the inhibition period clocking step starts the process of counting the reference clock at the time of the first change, and clocks the inhibition period on the basis of the count value; and
the period measurement step starts the process of counting the reference clock at the time of the second change, and measures the pulse period on the basis of the count value.
3. The pulse period measurement method of claim 2 , the method being used in controlling the pulse period and bringing the period to a target period; wherein
the sampling period is variably set in accordance with the target period.
4. The pulse period measurement method of claim 3 , wherein
the sampling period is proportional to the target period; and
the count value of the reference clock in the inhibition period is set to a constant value.
5. The pulse period measurement method of claim 1 , wherein
the inhibition period is set in accordance with the assumed value of the period of chattering produced at the pulse ends.