Rockwell Automation 20-750-PBUS Profibus DPV1 Option Module - Manual (Page 53)

Rockwell Automation Publication 750COM-UM004B-EN-P - September 2012 53
Using the I/O Chapter 5
Using Reference/Feedback The Reference is a 32-bit REAL (floating point) piece of control data produced
by the controller and consumed by the option module. The Feedback is a 32-bit
REAL (floating point) piece of status data produced by the option module and
consumed by the controller.
• Reference word is always the second 32-bit word in the output image.
• Feedback word is always the second 32-bit word in the input image.
The Reference and Feedback 32-bit REAL value represents drive speed. The
scaling for the speed Reference and Feedback are dependent on drive Parameter
300 - [Speed Units]. For example, if Parameter 300 is set to Hz, a 32- bit REAL
Reference value of ‘30.0’ would equal a Reference of 30.0 Hz. If Parameter 300 is
set to RPM, a 32- bit REAL Reference value of ‘1020.5’ would equal a Reference
of 1020.5 RPM. Note that the commanded maximum speed can never exceed the
value of drive Parameter 520 - [Max Fwd Speed].
Table 4 shows example
References and their results for a PowerFlex 750-Series drive that has its:
• Parameter 300 - [Speed Units] set to Hz.
• Parameter 37 - [Maximum Freq] set to130 Hz.
• Parameter 520 - [Max Fwd Speed] set to 60 Hz.
When Parameter 300 - [Speed Units] is set to RPM, the other parameters are also
in RPM.
Table 4 - PowerFlex 750-Series Drive Example Speed Reference/Feedback Scaling
Using Datalinks A Datalink is a mechanism used by PowerFlex drives to transfer data to and from
the controller. Datalinks allow a drive parameter value to be read or written to
without using a Profibus DPV1 Service. When enabled, each Datalink occupies
one 32-bit word in a ControlLogix controller, providing a mirror of the
PowerFlex 750-Series drive data value that the Datalinked parameter represents.
The following rules apply when using PowerFlex 750-Series drive Datalinks:
• The target of a Datalink can be any Host parameter, including those of a
peripheral. For example, drive parameter 535 - [Accel Time 1] can be the
target of any or all option modules installed in the drive.
Network
Reference Value Speed Command
Value
(2)
(2) For this example, drive parameter 300 - [Speed Units] is set to Hz.
Output Speed Network Feedback
Value
130.0 130 Hz 60 Hz
(3)
(3) The drive runs at 60 Hz instead of 130 Hz or 65 Hz because drive Parameter 520 - [Max Fwd Speed]
sets 60 Hz as the maximum speed.
60.0
65.0 65 Hz 60 Hz
(3)
60.0
32.5 32.5 Hz 32.5 Hz 32.5
0.0 0 Hz 0 Hz 0.0
-32.5 (1)
(1) The effects of values less than 0.0 depend on whether the PowerFlex 750 - Series drive uses a
bipolar or unipolar direction mode. See the drive documentation for details.
32.5 Hz 32.5 Hz 32.5