Agilent Technologies VXI E1439 - Manual (Page 102)

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Agilent E1439 Programmer's Reference
Functions listed alphabetically
when dataType is set to AGE1439_REAL and there is a non-zero center frequency the data scale
value is doubled for consistent spectrum measurements
dataTypePtr points to the current value of the dataType parameter.
mode selects whether the Agilent E1439's data collection operates in block mode or continuous mode.
AGE1439_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.
AGE1439_CONTINUOUS means that a single arm and trigger event starts a measurement which
runs continuously with no gaps between output data blocks. The measurement continues as long
as the data is read out fast enough to prevent overflow in the output FIFO. The continuous mode is
useful for continuous signal processing applications where data gaps are unacceptable.
modePtr points to the current value of the mode parameter.
port determines which output port is used to take data from the Agilent E1439 module.
Setting port to AGE1439_VME means the data is to be output using standard VME register reads.
This is the instrument default.
Setting port to AGE1439_LBUS means the data is to be output as a byte-serial data stream via the
VXI local bus (Agilent E1439D only) . When using the local bus port the module immediately to
the right of the Agilent E1439 must be capable of receiving the local bus byte sequence.
Setting port to AGE1439_FIBER means the filtered ADC data is to be transmitted as a serial data
stream over the fiber interface.
portPtr points to the current value of the port parameter.
resolution selects data resolution of either 12 or 24 bits by using resolution values of AGE1439_12BIT or
AGE1439_24BIT respectively. Choosing 12-bit precision allows for more samples in the FIFO
memory. Choosing 24 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 12 bit
resolution whenever the age1439_filter_setup function specifies a signal bandwidth greater than
10 MHz. 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, you should use the 24-bit
data resolution.
resolutionPtr points to the current value of the resolution parameter.
Comments
The following table summarizes the output word or byte sequence for each combination of
dataType, resolution, and port parameters: