VTI Instruments VM3608A, User Manual

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VM3608A/3616A Programming 51
The parameters passed to this function are the trigger source, trigger slope, voltage level value,
channel list and the number of channels in the channel list. Executing this function will program
the DAC at the voltage level. This function calls two other 'core' VXI
plug&play functions and is
an example of how to group them together. If the trigger source is set to AUTO, the output will be
immediately updated. If the trigger is set to anything else, that event must take place for the output
to update.
O
UTPUTTING FROM THE
S
CAN
L
IST
Up to 512 voltage level elements can be loaded into a scan list and the DAC can be programmed to
step through the list. A trigger event will cause the output of the DAC to be updated respective of
the value of the next index. Once the end of the list is reached, the DAC can either loop back to the
beginning of the list and repeat its sequence, or it can stop updating once the end is reached. To
program the scan list parameters, a
VXIplug&play application function has been provided. It is
important to note that the scan list is not used when the instrument is set to the ARB or FIFO
mode.
Vtvm3616_SetupScanListParameters
The parameters passed to this function are the channel number, mode (off, on, or loop), index in
the list where the DAC will either loop back or stop, voltage list (scan list values) and the number
of entries in the scan list.
Vtvm3616_ConfigTrigParameters
The trigger parameters should also be set to indicate how the scan list index will be advanced and
the output subsequently updated.
The scan list is limited in its update rate capabilities because it is interrupt driven.
O
UTPUTTING AN
A
RBITRARY
W
AVEFORM
To output an arbitrary waveform, it is important to understand the concept of traces, segments and
sequences . A 100-point sine wave, a 200-point triangle wave, a 300-point ramp function and a 300
point sine/triangle waveform are examples of traces. Up to 16 channels (8 for the VM3608A) can
be programmed in the ARB mode. A segment describes what each channel is outputting at a
particular point in time based on the trace data loaded for that particular channel. A segment can
contain up to
n traces, where n is the number of channels set to ARB mode.
Each defined segment is assigned a size, or number of points that it contains. This size is consistent
for all channels. The segment size always contains at least the number of data points of its largest
trace that is loaded. For example, if the following continuous outputs are desired
Channel 1 - 100 point sine wave
Channel 2 - 200 point triangle wave
Channel 3 - 300 point ramp function