Rockwell Automation Publication 1444-UM001D-EN-P - June 2018 391
CIP Objects Appendix A
Channel Select
The host sends the following CM Record Request Parameters as part of an
0x4C service request.
Table 119 - SpecialRequest Description (CM Record Request Parameters)
Bit Description
0 SR_MAG_PHASE Set to request phase (see Phase Data on page 334) and magnitude data from an FFT buffer, otherwise just
magnitude data is returned.
1 and 2 Reserved
3 SR_FILTER_LO Set bit to specify that if samples are decimated, either by specifying a lower FMAX
(1)
or by synchronous
resampling, then 37.5% of the unfiltered FFT lines are returned.
If bits 3 and 4 are both set, then the firmware automatically determines the number of returned FFT lines,
based on applied filtering.
(2)
4 SR_FILTER_HI Set bit to specify that if samples are decimated, either by specifying a lower FMAX
(1)
or by synchronous
resampling, then 62.5% of the unfiltered FFT lines are returned.
If bits 3 and 4 are both set, then the firmware automatically determines the number of returned FFT lines,
based on applied filtering
(2)
.
5 SR_EXTENDED Set bit to specify that if samples are not decimated or synchronously resampled that 112.5% of the unfiltered
FFT lines are returned.
When not set, 100% of FFT lines are returned for samples that are not decimated nor synchronously sampled.
IMPORTANT Recommended use is to set bits 3, 4 and 5. This setting makes sure that in all cases the maximum number of
lines are returned that are, in all cases, free of any filter attenuation or potential aliasing effects.
(1) The FMAX and FFT Lines presented in the AOP assume that bits 3, 4 and 5 are set. If other selections are made, then the FMAX or the number of FFT lines of a downloaded FFT does not always reflect
that presented in the AOP.
(2) When automatically deciding the factor to apply to decimated or synchronously resampled data, the firmware applies the SR_FILTER_LO (37.5%) factor when the -24 dB/octave filter is applied, and
the SR_FILTER_HI (62.5 %) factor with the -48 dB/octave or the -60 dB/octave filters are applied.
Data that is decimated on the Alternate Path always applies the -48 dB/octave filter. The applied filter on the primary path is the -24 dB/octave filter except when either of the Aeroderivative
Measurement Types are selected, in which case it applies the -60 dB/octave filter.
Bit 01234567
Channel 0123 Reserved
Byte Offset
Within Structure
Structure Member Data Type Description
0 SessionInstance USINT The host copies the SessionInstance returned here into each subsequent CM Record Request. Up to
three instances are supported.
1 DynamicChannel USINT Indicates the dynamic channel for this record. Channels 0 though 3 are valid channels.
2 CompletedRecords UINT Incremented each time that another complete record has been transferred.
There are often several packets per completed record.
4 RecordSize UDINT For a given session the RecordSize.
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