Rockwell Automation 1769-SM1 Compact I/O to DPI/SCANport Module - Manual (Page 53)

Understanding the I/O Image 4-5
A Datalink is a mechanism used by PowerFlex drives to transfer data to
and from the controller. Datalinks allow a parameter value to be changed
without using an Explicit Message. When enabled, each Datalink
consumes either two 16-bit or 32-bit words in both the input and output
image depending on its size. The size of Datalinks (16-bit words or
32-bit words) is determined by the drive and displayed with Parameter
06 - [Datalink Size 1], Parameter 23 - [Datalink Size 2], and
Parameter 40 - [Datalink Size 3] in the 1769-SM1 module.
Rules for Using Datalinks
• Each set of Datalink parameters in a PowerFlex drive can be used by
only one module. If more than one module is connected to a single
drive, multiple modules must not try to use the same Datalink.
• Parameter settings in the drive determine the data passed through the
Datalink mechanism. Refer to the documentation for your drive.
• When you use a Datalink to change a value, the value is not written
to the Non-Volatile Storage (NVS). The value is stored in volatile
memory and lost when the drive loses power. Thus, use Datalinks
when you need to change a value of a parameter frequently.
32-Bit Parameters using 16-Bit Datalinks
To read (and/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 09 - [Elapsed MWh] in a
PowerFlex 70 drive, both Datalink A1 and A2 are set to “9.” Datalink A1
will contain the least significant word (LSW) and Datalink A2 will
contain the most significant word (MSW). In this example, the parameter
09 value of 5.8 MWh is read as a “58” in Datalink A1.
Using Datalinks
Datalink Most/Least Significant Word Parameter Data (decimal)
A1 LSW 09 58
A2 MSW 09 0