Measurement Computing Data Translation DT3010 Series, User Manual, Page: 134 / 232

Principles of Operation
133
Specify internal cascade mode in software. The rising edge of the clock input signal is active.
Through software, specify the clock source as internal and the frequency at which to pace the
counter/timer operation (this is the frequency of the clock output signal). The maximum
frequency that you can specify for the clock output signal is 10 MHz. For a 32-bit cascaded
counter, the minimum frequency that you can specify for the clock output signal is 0.00465 Hz,
which corresponds to a rate of once every 215 seconds.
Note: In software, specify the clock input and gate input for the first counter in the cascaded
pair. For example, if counters 1 and 2 are cascaded, specify the clock input and gate input for
counter 1.
Gate Types
The active edge or level of the gate input to the counter enables counter/timer operations. The
operation starts when the clock input signal is received. DT3010 Series boards provide the
following gate input types:
• None – A software command enables any specified counter/timer operation immediately
after execution. This gate type is useful for all counter/timer modes.
• Logic-low level external gate input – Enables a counter/timer operation when the
external gate signal is low, and disables the counter/timer operation when the external
gate signal is high. Note that this gate type is used only for event counting, frequency
measurement, and rate generation; refer to
page 135 for more information on these modes.
• Logic-high level external gate input – Enables a counter/timer operation when the
external gate signal is high, and disables a counter/timer operation when the external
gate signal is low. Note that this gate type is used only for event counting, frequency
measurement, and rate generation; refer to
page 135 for more information on these modes.
• Falling-edge external gate input – Enables a counter/timer operation on the transition
from the high level to the low level (falling edge). In software, this is called a low-edge
gate type. Note that this gate type is used only for one-shot and repetitive one-shot mode;
refer to
page 143 for information on these modes.
• Rising-edge external gate input – Enables a counter/timer operation on the transition
from the low level to the high level (rising edge). In software, this is called a high-edge
gate type. Note that this gate type is used only for one-shot and repetitive one-shot mode;
refer to
page 143 for information on these modes.
Specify that gate type in software.
Table 12 lists the screw terminals that correspond to the gate input signals of each
counter/timer.