7-4 | ni.comChapter 7 CountersYou can calculate the pulse width by multiplying the period of the Source signal by the numberof edges returned by the counter.A pulse-width measurement will be accurate even if the counter is armed while a pulse train isin progress. If a counter is armed while the pulse is in the active state, it will wait for the nexttransition to the active state to begin the measurement.Refer to the following sections for more information about M Series pulse-width measurementoptions:• Single Pulse-Width Measurement• Buffered Pulse-Width MeasurementSingle Pulse-Width MeasurementWith single pulse-width measurement, the counter counts the number of edges on the Sourceinput while the Gate input remains active. When the Gate input goes inactive, the counter storesthe count in a hardware save register and ignores other edges on the Gate and Source inputs.Software then reads the stored count.Figure 7-5 shows an example of a single pulse-width measurement.Figure 7-5. Single Pulse-Width MeasurementBuffered Pulse-Width MeasurementBuffered pulse-width measurement is similar to single pulse-width measurement, but bufferedpulse-width measurement takes measurements over multiple pulses.The counter counts the number of edges on the Source input while the Gate input remains active.On each trailing edge of the Gate signal, the counter stores the count in a hardware save register.A DMA controller transfers the stored values to host memory.SOURCEGATECounter ValueHW Save Register1022Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
