Two methods are used for the frequency measurement.
1. Measure the input pulse frequency of specified counter:
The DRV_CounterFreqStart function starts the frequency measurement. When it is running, the DRV_CounterFreqRead function can be used to repeatedly measure the frequency. Call DRV_CounterReset function to stop the frequency measurement operation.
2. Measure both the high and low period of the input pulse:
The DRV_PWMStartRead function starts the pulse width measurement. Call DRV_CounterReset function to stop the pulse width measurement operation.
Notes:
a. There are two kinds of chips that are used in DA&C cards: Intel 8254 and AMD Am9513A.
b. AMD Am9513A chip uses gate mode control to attain a highly accurate frequency measurement. Frequency=number of samples/gate period
c. For the Intel 8254 chip, software gate mode is used.