VTI Instruments Corp.
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EX1629 Programming
The synchronization mode on a slave device is set to VTEX1629_SYNC_MODE_SLAVE and the
trigger bus line that is to be used to input the synchronization signal is specified using the
vtex1629_set_sample_clock_source
inLine
parameter.
Trigger Source
An EX1629 device can utilize a variety of trigger sources. The simplest is the immediate trigger
source. This causes the trigger state machine to bypass the TRIG layer and automatically begin to
acquire data. The device can also be configured to receive its trigger signal from either the positive
or negative edge transition of one of the LXI Trigger Bus lines. The final, and most complicated,
configuration is to generate a trigger signal based on a specified pattern of conditions. A
standalone device will either utilize an immediate or pattern trigger source. A slave device will
either also utilize an immediate trigger source or will specify a trigger bus line to receive a pattern
trigger source that is generated by a master device. The trigger source is specified using the
vtex1629_set_trigger_source function.
The vtex1629_set_pattern_trig_configuration function is used to configure the trigger pattern for a
master or standalone device that is using a pattern trigger source. This function can be used to
specify a combination of LXI Trigger Bus, digital I/O, timer, and software trigger events that will
generate a trigger event. In addition to the LXI Trigger Bus lines that may be used as pattern
inputs, a trigger bus line must be used to output the pattern trigger events. This line is specified
using the vtex1629_set_pattern_trig_configuration function’s
lxiOutput
parameter. This output
can either be used within the device or can be output to other devices using the external trigger
bus. As with the sample clock and synchronization signal configurations, the same LXI Trigger
Bus line can be used by the device for its trigger source or another trigger bus input can be
specified using the
lxiInput
parameter. In most cases, the
lxiInput
and
lxiOutput
parameters will
be the same. In a star configuration, however, the trigger event might be output on one LXI
Trigger Bus line and back in on a different trigger bus line.
The vtex1629_set_lxibus_configuration function must be used to configure the
lxiOutput
line as
an output with either internal only scope (if the signal will only be used within the device) or
external and internal transmission scope (if the line will be output to other devices). If the
lxiInput
parameter is different from the
lxiOutput
parameter, the trigger bus line specified by
lxiInput
must be configured as an input with external and internal transmission scope. Other LXI Trigger
Bus lines that are used for pattern inputs must be properly configured as inputs with external and
internal transmission scope.
Arm Source
The arm source is configured in the same manner as the trigger source. It utilizes the
vtex1629_set_arm_source and vtex1629_set_pattern_arm_configuration functions.
Standalone (Single Instrument) Example Configuration
The standalone configuration is suitable when only one instrument is required for the data
acquisition or if synchronization of multiple instruments is not required. It uses the instrument’s
internal oscillator for acquisition. The sample code that is provided performs the following tasks:
Sets the number of samples to acquire on a trigger to 100 (one second’s worth with the
100 Sa/s sample rate)
Reset the trigger system to return the trigger bus to its default configuration
Sets the Trigger to Immediate
Sets the Arm to Immediate
Sets the internal ADC clock
Sets the internal ADC synchronization
