Chapter 7 __________________________________________________ Host Computer Commands
VAISALA______________________________________________________________________ 259
The discarded output data are not in fact lost. Rather, the data are
eventually replaced with an equal number of zeros. Each time the RVP900
discards an output word, it also increments an internal 24-bit count. When
FIFO space becomes available in the future, the processor replaces all of
the missing data with zero-valued placeholders.
Writing when the FIFO is full can be particularly useful if the new
command is a RESET which calls for clearing of the output FIFO. When
the RESET is processed, all past and present output data are discarded,
leaving the RVP900 output section completely empty. This is useful
whenever the processor has pending output data which the user wants to
truly throw away.
7.1 No-Operation (NOP)
This single-word instruction is simply ignored by the the Signal Processor.
The NOP is useful when a number of words are to be flushed through the
RVP900 with no side effects.
0916-066
7.2 Load Range Mask (LRMSK)
This command informs the signal processor of the ranges at which data are
to be collected. An arbitrary set of range bins are selected via an 8192-bit
mask. The Nth bit in the mask determines whether data are acquired and
processed at a range equal to RES x (N-1). The Range resolution is
specified by a TTY setup question (see Section 4.2.5 Mt<n>— Triggers for
Pulsewidth #n on page 117), in the range 25 through 1000 meters. Any
collection of ranges may be chosen from integer multiples of that distance.
The example below is given for the default resolution of 125 meters. The
range mask is passed to the RVP8 packed into 512 16-bit words. The least
significant bit of each packed word represents the nearest range, and the
most significant bit represents the furthest range in each group of 16.
According to the range bins that are selected in the mask, the signal
processor computes and stores internally a range normalization table
which is later used to convert receiver intensity levels into reflectivity
levels in dBZ. Note that the LRMSK command implicitly specifies the
number of bins to be processed and output. The maximum bin count is
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