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E1437A User's Guide
VXI plug&play Programming Reference
dType determines whether the E1437 collects and returns real or complex data. Setting
this parameter to HPE1437_REAL causes only the real part of the data to be returned
for each sample. HPE1437_COMPLEX causes the real data followed by the imaginary
data to be returned in each sample. Normally, if the frequency set with the
hpe1437_frequency_setup function is zero, the type should be set to
HPE1437_REAL since the imaginary component of each sample is zero anyway. When
non-zero center frequencies are used the type should normally be set to
HPE1437_COMPLEX. Otherwise the imaginary component of the signal will be lost.
dTypePtr points to the current value of the dType parameter.
resolution selects data resolution of either 16 or 32 bits by using resolution values of
HPE1437_16BIT or HPE1437_32BIT respectively. Choosing 16-bit precision allows
for more samples in the FIFO memory. Choosing 32 bits allows more dynamic range.
Because of the broadband white noise present on the input of the analog-to-digital
converter, it is normally sufficient to use 16 bit resolution whenever the
hpe1437_filter_setup function specifies a signal bandwidth greater than 250 kHz. For
narrower bandwidths much of the broadband white noise is filtered out, resulting in
lower noise in the output data. To take advantage of this lower noise, the 32-bit data
resolution should be used.
resolutionPtr contains the current value of the resolution parameter.
mode selects whether the E1437's data collection operates in block mode or
continuous mode. HPE1437_BLOCK selects block transfer mode in which the
measurement is halted after each block of data. To start collection of the next data
block the module must be armed and triggered again. This mode is used whenever each
block of data is to be associated with an individual trigger "event".
HPE1437_CONTINUOUS means that a single arm and trigger event starts a
measurement which runs continuously with no gaps between output data blocks. As
long as the data is read out fast enough to prevent overflow in the output FIFO, the
measurement will continue. The continuous mode is useful for continuous signal
processing applications where data gaps are unacceptable.
modePtr contains the current value of the mode parameter.continuous mode;selecting
blocksize determines the number of sample points in each output data block. The
range of available block sizes depends on the number of bytes required for each sample.
The command accepts any number between 1 and memory size (in bytes)/2. The actual
number used is the first integer power of 2 equal to or larger than the requested
blocksize. If the requested block size falls outside the range shown in the table the
closest valid value will be used and a status register flag (bit 6) will be set indicating a
setup error. If a subsequent change in another parameter permits a block size closer to
the originally requested value, the module will adjust the block size to that value.
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