Chapter 5
66
C/T Clock Sources
The following clock sources are available for the counter/timer:
•
Internal clock
– Through software, specify the clock source as internal, and specify the
frequency at which to pace the counter/timer operation. The frequency of the internal
C/T clock can range from 60 Hz to 6 MHz.
•
External clock
– An external clock is useful when you want to pace counter/timer
operations at rates not available with the internal clock or if you want to pace at uneven
intervals.
Connect an external clock with a maximum recommended frequency of 6 MHz to the
Counter 0 In signal on a DT9816 Series module. Using software, specify the C/T clock
source as external, and specify a clock divider between 2 and 65534 to determine the
actual frequency at which to pace the counter/timer operation. For example, if you
connect a 6 MHz external C/T clock and use a clock divider of 2, the resulting C/T output
frequency is 3 MHz. Counter/timer operations start on the falling edge of the Counter 0 In
signal.
Note:
This signal has a 22.1 k
Ω
pull-up to +5 V. Therefore, when this pin is unconnected,
the signal goes to +5 V.
Gate Types
The edge or level of the Counter 0 Gate signal determines when a counter/timer operation is
enabled. Using software, you can specify one of the following gate types:
•
None
−
A software command enables any counter/timer operation immediately after
execution.
•
Logic-high level external gate input
−
Enables a counter/timer operation when Counter
0 Gate is high, and disables a counter/timer operation when Counter 0 Gate is low. Note
that this gate type is used for event counting and rate generation modes; refer to
for more information about these modes.
Pulse Duty Cycles
Counter/timer output signals from a DT9816 Series module are high-to-low going signals.
The low portion of the total pulse output period is the active portion of the counter/timer
clock output signal.
The duty cycle (or pulse width) indicates the percentage of the total pulse output period that is
active. In rate generation mode, the duty cycle is fixed at 50% for the DT9816 Series modules.
illustrates a high-to-low going output pulse with a duty cycle of 50%.
Содержание DT9816 Series
Страница 1: ...DT9816 Series UM 21336 X User s Manual Title Page ...
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Страница 8: ...Contents 8 ...
Страница 12: ...About this Manual 12 ...
Страница 13: ...13 1 Overview Key Hardware Features 14 Supported Software 16 Getting Started Procedure 19 ...
Страница 20: ...Chapter 1 20 ...
Страница 21: ...Part 1 Getting Started ...
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Страница 44: ...Chapter 3 44 ...
Страница 54: ...Chapter 4 54 ...
Страница 55: ...Part 2 Using Your Module ...
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Страница 57: ...57 5 Principles of Operation Analog Input Features 59 Digital I O Features 64 Counter Timer Features 65 ...
Страница 81: ...81 7 Troubleshooting General Checklist 82 Technical Support 84 If Your Module Needs Factory Service 85 ...
Страница 86: ...Chapter 7 86 ...
Страница 102: ...Appendix B 102 ...
Страница 108: ...Index 108 ...