Rockwell Automation 20-COMM-ER 20-COMM-ER Dual-Port EtherNet/IP Communication Adapter User Manual - Manual (Page 86)

86 Rockwell Automation Publication 20COMM-UM015B-EN-P - July 2013
Chapter 5 Using the I/O
The controller in the system sends a reference to the SMC, but it is not used for
control purposes in the current release.
The SMC products use the feedback to send motor current information.
Using Datalinks
A Datalink is a mechanism used by PowerFlex drives and SMCs to transfer data
to and from the controller. Datalinks allow a device parameter value to be read or
written without using an Explicit Message. When enabled, each Datalink
occupies two 16-bit or 32-bit words in both the input and output image. Use
adapter Parameter 21 - [Datalink Size] to determine whether the drive uses 16-
bit or 32-bit words for Datalinks.
Rules for Using Datalinks
• Each set of Datalink parameters in a device can be used by only one
adapter. If more than one adapter is connected to a single device, multiple
adapters cannot use the same Datalink.
• Parameter settings in the device determine the data passed through the
Datalink mechanism. See the documentation for your device.
• When you use a Datalink to change a value, the value is NOT written to
the Nonvolatile Storage (NVS). The value is stored in volatile memory and
lost when the device loses power. Therefore, use Datalinks when you need
to change a value of a parameter frequently.
Using 16-Bit Datalinks to Read/Write 32-Bit Parameters
This subsection only pertains to the SMC Flex and PowerFlex 70 (SC or EC),
PowerFlex 700 (SC), and PowerFlex 700H drives which use 16-bit Datalinks. To
read or write a 32-bit parameter using 16-bit Datalinks, typically both Datalinks
of a pair (A, B, C, D) are set to the same 32-bit parameter. For example, to read
parameter 10 - [Elapsed Run Time] in a PowerFlex 70 drive, both Datalink A1
Out (Parameter 310) and Datalink A2 Out (Parameter 311) are set to ‘10’.
Datalink A1 Out will contain the least significant word (LSW) and Datalink A2
Out will contain the most significant word (MSW).
TIP For PowerFlex 700 VC drives, firmware 3.xxx or later, parameter 299 - [DPI Fdbk Select]
enables you to select the feedback data coming from the drive over DPI. The default is
‘Speed Fdbk’ in Hz or RPM determined by parameter 079 - [Speed Units]. The data
selection for parameter 299 is also displayed on the 1st line of the HIM and on
DriveExplorer and DriveExecutive software screens in the drive status area of the screen.