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On the DT9837 module, the clock frequency is fixed at 46.875 kHz. On the DT9837A module,
you can program the clock frequency to value between 10 kHz and 52.734 kHz. On the
DT9837C module, you can program the clock frequency to value between 10 kHz and
96.0 kHz.Use software to specify an internal clock source and to specify the clock frequency
for the analog output subsystem.
Internally, the value that you specify for the analog output clock frequency is multiplied by
512 to set the oscillator on the module. The maximum timebase for the DT9837 is 24 MHz; the
maximum timebase for the DT9837A and DT9837C is 27 MHz.
Due to the group delay of the Delta-Sigma D/A converter, the DT9837 requires 34 clock
pulses, while the DT9837A and DT9837C modules require 29 clock pulses once the analog
output sample clock is started before the first D/A conversion is completed.
Output Conversion Modes
The DT9837, DT9837A, and DT9837C modules support single-value and waveform analog
output operations. The DT9837A and DT9837C modules also support continuous analog
output operations. This section describes each of these conversion modes.
Note: The DT9837A also provides the ability to read the value of the analog output channel
in the analog input data stream. Refer to
Single-Value Mode
Single-value mode is the simplest to use but offers the least flexibility and efficiency. Use
software to specify the analog output channel that you want to update, and the value to
output from that channel. The value is output from the specified channel immediately.
For a single-value operation, you cannot specify a clock source, trigger source, or buffer.
Single-value operations stop automatically when finished; you cannot stop a single-value
operation.
Note: On the DT9837 module, ensure that no analog input operations are running before
performing an analog output operation or an error will be reported.
Waveform Generation Mode
Waveform generation mode is supported on the DT9837, DT9837A, and DT9837C modules. In
this mode, a waveform, which is specified in a single buffer, is output repetitively.
On the DT9837, allocate a buffer less than or equal to 8192 samples, and then fill the buffer
with the waveform that you want to output. On the DT9837A and DT9837C modules, you can
allocate a buffer of any size, and then fill the buffer with the waveform that you want to
output.
page 79
for more information.
Principles of Operation
77
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