Rockwell Automation Publication 750COM-UM009A-EN-P - May 2017 91
Using the I/O Chapter 4
Using Datalinks
A datalink is a mechanism that is 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 an explicit message. When enabled, each datalink
occupies one 32-bit word in a ControlLogix controller.
The following rules apply when using PowerFlex 755T drive datalinks:
• The target of a datalink can be any Host parameter, including host
parameters of a peripheral. For example, drive 10:1915 - [VRef Accel
Time 1] can be the target of the built-in EtherNet/IP interface and any
or all option modules that are installed in the drive.
•The settings of 0:321…336 - [DL From Net 01…16] and
0:340…355 - [DL To Net 01…16] determine the data that is passed
through the datalink mechanism of the drive.
• When an I/O connection that includes datalinks is active, those
datalinks being used are locked and cannot be changed until that I/O
connection becomes idle or inactive.
• 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 drive loses power. Use datalinks to change the value of
a parameter frequently.
Datalinks for PowerFlex 755T peripherals are locked when the peripheral has
an I/O connection with a controller. For example, the built-in EtherNet/IP
interface on PowerFlex 755T drives only, and option modules such as an
encoder or a communication module. When a controller has an I/O
connection to the drive, the drive does not allow anything that could change
the makeup of the I/O connection in a running system. For example, a reset to
defaults and configuration download. The I/O connection with the controller
must first be disabled to allow changes to the respective datalinks.
Depending on the controller being used, the I/O connection can be disabled
by doing the following:
• Inhibiting the module in Studio 5000 or RSLogix 5000 environment
• Putting the controller in Program mode
• Disconnecting the drive from the network
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