Data Translation DT9834 Series, Руководство пользователя

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Chapter 5
100
• One-shot
• Repetitive one-shot
Note: The active polarity for each counter/timer operation mode is software-selectable.
The following subsections describe these modes in more detail.
Event Counting
Use event counting mode if you want to count the number of rising edges that occur on the
Counter
n Clock input when the Counter n Gate signal is active (low-level or high-level). Refer
to page 98 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.
Using software, specify the counter/timer mode as event counting (count), the C/T clock
source as external, and the active gate type as low-level or high-level.
Make sure that the signals are wired appropriately. Refer to
page 57 for an example of connecting an event counting application.
Up/Down Counting
Use up/down counting mode if you want to increment or decrement the number of rising
edges that occur on the Counter
n Clock input, depending on the level of the Counter n Gate
signal.
If the Counter n Gate signal is high, the C/T increments; if the specified gate signal is low, the
C/T decrements.
Using software, specify the counter/timer mode as up/down counting (up/down), and the
C/T clock source as external. Note that you do not specify the gate type in software.
Make sure that the signals are wired appropriately. Refer to
page 58 for an example of connecting an up/down counting application.
Note: Initialize the counter/timer so that the C/T never increments above FFFFFFFFh or
decrements below 0.