Data Translation DT9834 Series, User Manual

Page: 103 / 186

Principles of Operation
103
Rate Generation
Use rate generation mode to generate a continuous pulse output signal from the Counter n
Out line; this mode is sometimes referred to as continuous pulse output or pulse train output.
You can use this pulse output signal as an external clock to pace other operations, such as
analog input, analog output, or other counter/timer operations.
The pulse output operation is enabled whenever the Counter n Gate signal is at the specified
level. While the pulse output operation is enabled, the counter outputs a pulse of the specified
type and frequency continuously. As soon as the operation is disabled, rate generation stops.
The period of the output pulse is determined by the C/T clock source (either internal using a
clock divider, or external). You can output pulses using a maximum frequency of 9 MHz (this
is the frequency of the Counter
n Out signal). Refer to page 98 for more information about the
C/T clock sources.
Using software, specify the counter/timer mode as rate generation (rate), the C/T clock
source as either internal or external, the clock divider (for an internal clock), the polarity of the
output pulses (high-to-low transition or low-to-high transition), the duty cycle of the output
pulses, and the active gate type (low-level or high-level). Refer to
page 99 for more
information about pulse output signals and to page 98 for more information about gate types.
Make sure that the signals are wired appropriately. Refer to page 61 for an example of
connecting a rate generation application.
One-Shot
Use one-shot mode to generate a single pulse output signal from the Counter n Out line when
the specified edge is detected on the Counter n Gate signal. You can use this pulse output
signal as an external digital (TTL) trigger to start other operations, such as analog input or
analog output operations.
After the single pulse is output, the one-shot operation stops. All subsequent clock input
signals and gate input signals are ignored.
The period of the output pulse is determined by the C/T clock source (either internal using a
clock divider, or external). Note that in one-shot mode, the internal C/T clock is more useful
than an external C/T clock; refer to
page 98 for more information about the C/T clock sources.
Using software, specify the counter/timer mode as one-shot, the clock source as internal
(recommended), the clock divider, the polarity of the output pulse (high-to-low transition or
low-to-high transition), and the active gate type (rising edge or falling edge). Refer to
page 99
for more information about pulse output types and to page 98 for more information about
gate types.
Note: In the case of a one-shot operation, a duty cycle of 100% is set automatically.