Allen-Bradley 20-COMM-M Modbus/TCP Adapter User Manual page 42

4-6 Using Modbus/TCP Function Codes
20-COMM-M Modbus/TCP Adapter User Manual
Publication 20COMM-UM014C-EN-P
Table 4.F Reference Registers
Register Description
Address
(1)
10003 Reference Lo
10004 Reference Hi
(1)
For a 16-bit Reference, you must write the complete 32-bit value.
The Reference value is a scaled engineering value; it is NOT in Hertz or
RPM. The Reference uses a "32767" scale. The "32767" endpoint of the
scale is equal to the value of parameter 55 - [Maximum Freq], which has a
default value of 130 Hz. For all PowerFlex 70/700 drives, default scaling is
0...15123 which is equal to 0...60.0 Hz. This is based on the formula
shown below. Reference scaling is limited by drive parameter 82 -
[Maximum Speed]. If the default value of 60 Hz. for parameter 82 -
[Maximum Speed] is changed, the speed Reference scaling also changes. To
determine Reference scaling, use:
(Parameter 82 / Parameter 55) * 32767 = Scaling
Using parameter 82 and 55 default values, speed Reference scaling is:
(60 Hz / 130 Hz) * 32767 = 15123
Therefore, 0...15123 = 0...60.0 Hz.
If parameter 82 - [Maximum Speed] is changed to 90 Hz, then:
(90 Hz / 130 Hz) * 32767 = 22685
Therefore, 0...22685 = 0...90.0 Hz.
A graphic representation of this Reference scaling is shown below:
130 Hz
90 Hz
60 Hz
0 Hz
0
Scaling = (Parameter 82 / Parameter 55) * 32767
For PowerFlex 70 EC drives (firmware v2.xxx or higher) or PowerFlex 700
VC drives (firmware v3.xxx or higher), parameter 298 - [DPI Ref Select]
was added to simplify scaling for the speed Reference. When parameter 298
- [DPI Ref Select] is set to its default "0" (Max Freq), the speed Reference
scaling is as shown above. However, when parameter 298 - [DPI Ref Select]
is set to "1" (Max Speed), the speed Reference scaling is equal to parameter
82 - [Max Speed]:
Therefore, 0...32767 = 0...60.0 Hz.
If parameter 82 - [Maximum Speed] is changed to 90 Hz, then:
Values
Bit 0...15 of 32-bit Reference or the whole 16-bit Reference
Bit 16...31 of 32-bit Reference
15123 22685
Parameter 82 = Scaling
90 Hz = 32767
32767