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Programmer’s Guide Page 45 of 66
3.11.8.4. Reading the histogram
The accumulated histogram can be read out using readMode = 9 (ReadModeHistogram). The dataType and
dataArraySize must be selected to correspond to the size of the histogram and its bins.
The waveform descriptor structure contains the value actualDataSize giving the total number of data bytes read. The
individual histogram bins will be able to contain accumulated sums of either 2**32, as ViUInt32, or 2**16, as
ViUInt16.
Histogram bin is 32 bits wide
31..0
Bin0
…
Histogram bin is 16 bits wide
31..16
15..0
Bin 1
Bin 0
…
…
3.11.9. Reading U1084A Peak
TDC
Waveforms and Histograms
3.11.9.1. Reading the histogram
Use „readMode‟ = 9 (ReadModeHistogram), „dataType‟ = 2 (ReadInt32) to read out the accumulated histogram. The
nbrSamples must be selected to correspond to the size of the histogram and its bins. Note that the value for
„nbrSamples‟ should correspond to the number of bins in the histogram to read, which may be different from the
configured number of samples in the acquisition if interpolation is enabled. For example, if you have configured
„NbrSamples’ to 1024 and „TdcHistogramHorzRes’ to 3 with AcqrsD1_configAvgConfig, there will be 2
3
= 8
bins per sample, for a total of 1024 * 2
3
= 8192 bins available for readout.
If vertical interpolation is used, the values of the bins should be interpreted as fixed point fractional values. This
means that, if „TdcHistogramVertRes’ is set to N, the actual amplitude of the bin is the raw unsigned integer value
divided by 2
N
.
Because the data array and transfer size may have to be realigned, the data array should be at least 16 bytes (4
samples) longer than the histogram data to read. To find the first valid sample in the data array, the data descriptor‟s
„indexFirstPoint‟ field must be used, which indicates the offset in samples of the first valid sample from the
beginning of the data array.
3.11.9.2. Reading the last acquired waveform
To facilitate the visualization and interpretation of the histogram data, the U1084A permits to read the last raw
waveform which contributed to the histogram, as 8 bit samples. This is done using readMode = 0 (ReadModeStdW)
with dataType = 0 (ReadInt8). The procedure is the same as the one described in 3.11.1 Reading Digitizer
Waveforms with the Universal Read Function.
3.11.10. Reading AP101/AP201 Analyzer Waveforms
3.11.10.1. Reading a Buffered Waveform Sequence
This section concerns AP101/AP201 Analyzers ONLY. In normal mode, you may read the acquired waveform(s) in
the same way as with any other digitizer, as described in the section 3.11, D1-style Data Readout, in the
Programmer‟s Guide.
In buffered mode, you must use the functions AcqrsD1_readData to read out the accumulated waveform sequence,
as a single data record. E.g. if you configured nbrSamples = 5000 and nbrSegments = 800, you should specify
segmentNumber = 0 and nbrSamples = 4‟000‟000.
Before reading the buffered data, you must switch to the other memory bank. Typically, you also would start a new
acquisition before readout, but it is not required. This is done automatically in the SSR mode as a consequence of the
call to AcqrsD1_processData with a non-zero flag value. It can also be done with a call to AcqrsD1_configMode
The read-function returns zero into the dataDesc variables horPos, tStampLo and tStampHi, since they are
unavailable in the context of a buffered waveform sequence.