Data Translation DT9812 Series, User Manual

Page: 73 / 124

Principles of Operation
73
Counter/Timer Operation Modes
The modules support the following counter/timer operation modes:
• Event counting
• Frequency measurement
• Edge-to-edge measurement
• Rate generation
Event Counting
Use event counting mode if you want to count the number of falling edges that occur on
Counter 0 In when the gate is active (high-level gate or software gate). Refer to
page 72 for
information about specifying the active gate type.
You can count a maximum of 4,294,967,296 events before the counter rolls over to 0 and starts
counting again.
For event counting operations, use software to specify the counter/timer mode as count, the
C/T clock source as external, and the active gate type as software or high-level.
Make sure that the signals are wired appropriately. Refer to page 39 for an example of
connecting an event counting application.
Frequency Measurement
Connect a pulse of a known duration to the Counter 0 Gate signal. Specify the active gate in
software (high level or low level). When the operation starts, read the number of counts that
occurred when the gate was active.
You can determine the frequency of the clock input signal using the following equation:
Frequency Measurement = Number of Events
Measurement
Period
Make sure that the signals are wired appropriately. Refer to page 40 for an example of
connecting a frequency measurement application.