Rockwell Automation 1440-SDM02-01RA XM-124 Standard Dynamic Measurement Module - Manuel (Page 147)

Rockwell Automation Publication 1440-UM001C-EN-P - May 2014 147
CIP Objects Appendix B
Services
(1) Attributes can only be set while the device is in Program mode. See the description of the Device Mode Object for more information.
Get_Spectrum_Chunk/Get_Waveform_Chunk
These services return a portion of the respective data structure. It is likely that the
spectrum and waveform data structures are too large to transfer over the network
in one message. These services let the data structures be transferred over the
network in smaller portions so that the explicit message buffer does not need to
be so large.
The Spectrum Data structure contains an array of values that, taken together, are
the output of the spectrum measurement performed by the Spectrum/Waveform
Measurement Object on the input signal. The size of the Spectrum Data
structure and format of the data array depends on the Data Format attribute. In
all cases, the spectrum data array values are normalized and must be converted to
floating point to obtain the true values.
The total size of the Spectrum Data structure in DWORD is:
• For Magnitude Data Format: 3 + (Number of Spectrum Lines / 2)
• For Complex Data Format: 3 + (Number of Spectrum Lines)
Table 69 - Spectrum Waveform Measurement Object Services
Service Code
Class/Instance Usage Name Description
0E
h
Instance Get_Attribute_Single Returns a single attribute.
10
h
Instance Set_Attribute_Single Sets a single attribute.
(1)
4B
h
Instance Get_Spectrum_Chunk Upload a portion of the current
Spectrum data.
4C
h
Instance Get_Waveform_Chunk Upload a portion of the current
Waveform data.
Table 70 - Spectrum Data Structure
Byte (DWORD) offset
within structure
Structure Member Data Type Description
0 (0) Number of Spectrum Lines UDINT Number of lines or bins in the spectrum data. This must be equal to the
Number of Spectrum Lines attribute setting. It is provided within this
structure to assist in determining the size of the structure.
4 (1) FMAX REAL The maximum frequency or order of the spectrum data.
This is the actual FMAX of the spectrum data and may vary from the FMAX
attribute setting.
8 (2) Amplitude Reference REAL Normalization factor
This factor is used to convert the normalized array data into floating point
values.
12 (3) Normalized Value Array Array of INT or UINT The normalized spectrum data points
These must be converted to floating point values using the Amplitude
Reference value. The Data Format attribute determines whether these are
INT or UINT and exactly what conversion must be applied.