Period/Rate Mode - 1794-VHSC

Period/rate mode determines the frequency of input pulses by counting the number of internal 5MHz clock pulses over a user-specified number of input signal pulses. At the end of the specified number of pulses, the module returns the frequency and the total number of pulses received.

A channel configured for period/rate mode acts as a period rate counter. An internal 5MHz clock is used as a frequency reference. This clock is gated by the incoming pulse train at the gate/reset input. The results of this gating action are the number of pulses or a frequency. The frequency is returned in the Ch0StoredCount and Ch1StoredCount members for channel 0 and word 2 and 3 for channel 1. The total pulses received value is stored in input file words 4 and 5 for channel 0 and words 6 and 7 for channel 1. Select the period/rate mode by setting the appropriate bits in word 0 of the configuration block.

1794-VHSC modules count the total number of pulses occurring at the Z (gate/reset) pin. This function is frequency-limited to 200Hz X the scalar value. You can reset this count by setting the ValueReset bit.