Rockwell Automation 20-COMM-M Modbus/TCP Adapter - Manual (Page 48)

4-12 Using Modbus/TCP Function Codes
20-COMM-M Modbus/TCP Adapter User Manual
Publication 20COMM-UM014C-EN-P
Writing Device Parameters
1. Verify that the Unit Identifier is set to “0” (zero).
2. Using Table 4.J and its associated formula, determine the value to use
for an adapter Indirect Parameter that points to the specific device
parameter you want to write. For example, suppose adapter Parameter
38 - [Indirect Par #1] is used and you want to write to drive Parameter
140 - [Accel Time 1]. In this case, set adapter Parameter 38 - [Indirect
Par #1] to a value of “140.”
3. Use Function Code 16 or 23 ( Table 4.A ) to write a desired value to the
specific device parameter(s). For this example, write a value of “20”
(2.0 seconds) to register addresses 10041 and 10042 for adapter Indirect
Parameter #1 Data as shown in
Table 4.K .
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 without accessing the specific parameter. When enabled, each
Datalink occupies two 16-bit or 32-bit words in both the input and output
image. Use adapter Parameter 22 - [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 PowerFlex drive can be used by
only one adapter. If more than one adapter is connected to a single drive,
multiple adapters cannot 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.
Reading Datalinks
Use the register addresses in Table 4.L to read Datalinks using Function
Code 03 or 23.