472 Rockwell Automation Publication 1444-UM001D-EN-P - June 2018
Appendix A CIP Objects
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.
Number of samples per revolution occupies the first byte, the remaining three
bytes are used for a scaled speed value (speed x 100). This format supports
speed values to 167,772.15 rpm with a resolution of two decimal places.
Example with 'data on the wire' of 0x 10DC7D05:
• 0x 10 = 16 samples per revolution
• 0x 057DDC = 359,900
• RPM = 359,900/100 = 3599 rpm (60 Hz)
Whether the data is asynchronous or synchronous can be known from the
identifier field. This data has the following format.
Bits Description
0...1 Measurement channel (0, 1, 2, 3) from which the data
originates
2 Data source (Transfer path 0 or 1)
3...4 Transfer path 0 data source (0 pre-filter, 1 mid-filter, 2
post filter)
5...6 Transfer path 1 data mode (bit 5 = 0 asynchronous, bit
5 = 1 synchronous then bit 6 indicates which tacho
was used.
7 Associated tacho source from the Normal CM Data
Object
8...15 Measurement engineering units (index not CIP code)
16...31 Reserved
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