Rockwell Automation Publication 750COM-UM009A-EN-P - May 2017 95
Chapter 5
Using Explicit Messaging
This chapter provides information and examples that explain how to use
Explicit Messaging with a ControlLogix® controller to configure and monitor
the interface and connected PowerFlex® 755TR, 755TL, 755TM drives, and
755TM Bus Supply.
For information on how to use a PLC-5®, SLC™ 500, or MicroLogix™ 1100/
1400 controller, see Controller Examples for EtherNet/IP Network
communication with PowerFlex 750-Drives, publication 750COM-AT001
.
See Chapter 4
for information about the I/O Image, the use of logic
command/status, reference/feedback, and datalinks.
Topic Page
About Explicit Messaging 96
Performing Explicit Messaging 98
ControlLogix Controller Examples 99
Ladder Logic Program to Read a Single Parameter 99
Formatting a Message to Read a Single Parameter 100
Ladder Logic Program to Write a Single Parameter 101
Formatting a Message to Write a Single Parameter 102
Ladder Logic Program to Read Multiple Parameters 103
Formatting a Message to Read Multiple Parameters 104
Ladder Logic Program to Write Multiple Parameters 106
Formatting a Message to Write Multiple Parameters 107
Explanation of Request and Response Data for Scattered Read Multiple Messaging 109
IMPORTANT The drive saves parameter values that are written through Scattered Write
messages into the drives nonvolatile storage (NVS). The NVS allows only a
limited number of write cycles before it cannot store data reliably. To avoid
reaching this limit, do not use the Scattered Write messages for continuous
changes to parameter values.
If a parameter value must be changed continuously, you can use the
datalinks that are associated with the Logix controller's I/O connection, or
you can use individual parameter write messages that store the values that
are written to random access memory (RAM) rather than nonvolatile storage
(NVS) (see class 0x93, instance attribute 10, on page 147
).
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