394 Rockwell Automation Publication 1444-UM001D-EN-P - June 2018
Appendix A CIP Objects
See Reading FFT Data on page 333 for details on how to calculate the FFT
from the read data.
Wa v e f o r m (eTWF, eTWF_ALARM)
See Reading TWF Data
on page 332 for details on how to calculate the TWF
from the read data.
Tach o (eTACHO, eTACHO_ALARM)
For FFT and TWF data
For asynchronous data, the actual sample period is transferred (REAL format).
For synchronous data, the same four bytes are used to transfer the number of
samples per revolution and an indicative speed for the transferred data.
Table 122 - Record Type Structures
Byte Offset
Within
Structure
Structure Member Data
Type
Description
0 TimestampNanoSec UDINT Subsecond accuracy.
4 TimestampSec UDINT Seconds since 1970.
8 SamplePeriodInSecs REAL Time period between samples.
12 Identifier DWORD Data source, mode, tacho source, and measurement units.
16 RelativeTime UDINT A 24-bit (micro-second) counter-value for finely aligning data.
See Reading Continuous Time Waveforms
on page 329 for
information on using this parameter.
20 ByteCount UDINT The size of the following array in bytes.
24 SampleArray REAL The array of waveform data values (samples).
Table 123 - Record Type Structures
Byte Offset
Within
Structure
Structure Member Data
Type
Description
0 TimestampNanoSec UDINT Subsecond accuracy.
4 TimestampSec UDINT Seconds since 1970.
8Reserved REAL
12 Reserved DWORD
16 Reserved UDINT
20 ByteCount UDINT The size of the following array in bytes.
24 TimingArray UDINT The array of tacho time values (24 bit, micro-second counter).
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