User manual

Programmer’s Guide Page 24 of 64
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• The value of the third argument to AcqrsD1_configMode must always be 0.
• When in Zero-Suppress mode, the following digitizer parameters are ignored:
• nbrSamples and nbrSegments of the function AcqrsD1_configMemory are replaced by “NbrSamples”
and “NbrSegments” in the function AcqrsD1_configAvgConfig.
• The value nbrSamples defines the target number of samples to acquire in each segment (trigger) before
zero-suppression is applied. The value of nbrSamples must be integer multiples of 2048 for U1084A in
dual-channel mode, and 4096 in single-channel mode. If the supplied value is not an integer multiple of the
above values, it is truncated to the next lower integer multiple. Thus, nbrSamples = 12000 will be truncated
to 10240 for a Dual-channel acquisition, and to 8192 for a Single-channel acquisition. You can query the
actual value with the function AcqrsD1_getAvgConfig.
• The value PreSamples guarantees a number of samples before the first one satisfying the threshold
condition. The value must be a multiple of 16 in Dual-channel mode, and a multiple of 32 in Single-channel
mode.
• The value PostSamples guarantees a number of samples after the last one satisfying the threshold condition.
The value must be a multiple of 16 in Dual-channel mode, and a multiple of 32 in Single-channel mode.
• The value MaxSamplesPerSegment determines the maximum number of actual data samples that will be
stored per segment after the zero-suppression is applied, per channel. Only samples that are actually retained
are counted. Any data above this index will be truncated. The actual number of samples stored in each
segement will depend on the signal, the threshold configuration and the value of maxSamplesPerSegment.
This parameter may be used to limit the amount of data stored in each segment (gate), which may be useful
in tuning the acquisition to avoid skipped triggers due to the time required to perform the data readout.
3.6.2. U1084 Zero-Supression mode – Threshold configuration
The U1084A Zero Suppress mode supports up to 128 different thresholds which are applied in sequence. For each
threshold, a sample position can be given from where to start applying this threshold.
Use the function AcqrsD1_configSetupArray() to configure the thresholds, passing a setupType value of 2, and a
pointer to an array of AqThresholdGateParametersU1084A structures in the setupData parameter. A different set
of threshold can be configured for each channel.
The AqThresholdGateParametersU1084A structure has the following fields:
Name
Type
Description
threshold
ViReal64
The threshold value to use, in Volts.
nextThreshSample ViUInt32 The index of the sample in the segment, at which the Zero Suppression
system should switch to the next threshold in the array.
Reserved
ViInt32
Reserved field, must be 0
The thresholds are applied in the order given in the setup array, each for a given duration. For example, if setupData
is defined as follows:
AqThresholdGateParametersU1084A setupData[4];
Then in each segment, setupData[0].threshold is applied from sample 0 (the first sample of the segment) up to
sample number setupData[0].nextThreshSample-1. Starting at sample number setupData[0].nextThreshSample, the
threshold setupData[1].threshold is used up to sample number setupData[1].nextThreshSample-1, etc.
The last entry in the setup array must have a value of 0xffffffff (2^32 - 1) for nextThreshSample, to indicate that it
will be applied up to the end of the segment. Except for this special value, all values of nextThreshSample must be a
multiple of 16 (for dual channel / non-combined operation) or 32 (for single-channel / combined x2 operation). In
addition, the value of nextThreshSample of each array element must be strictly greater than the value of
nextThreshSample of the preceding array element.