Measurement Computing Data Translation DT3034, User Manual

Page: 99 / 178

Chapter 6
98
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. DT3034 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 100 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 100 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 107 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 107 for information on these modes.
Specify that gate type in software.
Table 6 lists the screw terminals that correspond to the gate input signals of each
counter/timer.