Measurement Computing Data Acquisition Systems rev.10.4 - Manual (Page 215)

Function Usage
The term waveform/pattern output is used extensively throughout the entries for the
functions of the form daqDac…. This refers to an analog waveform output modes and/or
digital pattern output modes. These terms describe output to DAC and/or digital output
channels that are synchronously updated by a clock source defined by the application.
The frequency is set via the freq parameter and is dependent upon the clock source chosen for the selected
device. The clock source can be configured via the daqDacWaveSetClockSource function. The
waveform/pattern output update frequency is the rate at which samples are sent from the internal output FIFO
to a single output channel.
Setting the Output Update Frequency
The output update frequency is set via the freq parameter. This parameter sets the internal waveform/pattern
output pacer clock (in Hz) and represents the frequency at which all channels configured for waveform/pattern
output will be updated. Each time the configured waveform/pattern output pacer clock fires, a sample for each
channel will be loaded from the internal FIFO into the appropriate DAC or digital output device and output.
The frequency programmed using the freq function may not be obtainable. The reason for this is that either
the frequency specified is outside of the operating update frequency of the output pacer clock, or, due to the
resolution of the pacer clock, the frequency is not attainable. If the latter is the case, then the output pacer clock
will be programmed to the nearest attainable frequency. If the frequency is outside of the operating range of
the pacer clock, then an error will be generated. See the daqDacWaveGetFreq function for more
information on setting the output pacer clock frequency.
The specifications section of the device user’s manual provides the acceptable frequency values for the device.
Prototypes
C/C++
daqDacWaveSetFreq(DaqHandleT handle, DaqDacDeviceType deviceType, DWORD
chan, FLOAT freq);
Visual BASIC
VBdaqDacWaveSetFreq&(ByVal handle&, ByVal deviceType&, ByVal chan&, ByVal
freq!)
Program References
DAQDACEX02.CPP, DAQDACEX03.CPP
Programmer’s Manual 908494 Daq API Command Reference 4.4-33