11.6 RS485: FC Protocol Parameter
Examples
11.6.1 Writing a Parameter Value
Change
parameter 4-14 Motor Speed High Limit [Hz]
to 100
Hz.
Write the data in EEPROM.
PKE=E19E hex - Write single word in
parameter 4-14 Motor
Speed High Limit [Hz]
.
IND=0000 hex
PWE
high
=0000 hex
PWE
low
=03E8 hex - Data value 1000, corresponding to 100
Hz, see
.
E19E H
PKE
IND
PWE
high
PWE
low
0000 H 0000 H 03E8 H
130BA092.10
Illustration 11.12 Telegram
NOTICE
Parameter 4-14 Motor Speed High Limit [Hz]
is a single
word, and the parameter command for write in EEPROM
is E. Parameter number
parameter 4-14 Motor Speed High
Limit [Hz]
is 19E in hexadecimal.
119E H
PKE
IND
PWE
high
PWE
low
0000 H 0000 H 03E8 H
130BA093.10
Illustration 11.13 Response from Master-to-Slave
11.6.2 Reading a Parameter Value
Read the value in
parameter 3-41 Ramp 1 Ramp Up Time
.
PKE=1155 Hex - Read parameter value in
parameter 3-41 Ramp 1 Ramp Up Time
IND=0000 hex
PWE
high
=0000 hex
PWE
low
=0000 hex
1155 H
PKE
IND
PWE
high
PWE
low
0000 H 0000 H 0000 H
130BA094.10
Illustration 11.14 Parameter Value
If the value in
parameter 3-41 Ramp 1 Ramp Up Time
is
10 s, the response from the slave to the master is:
130BA267.10
1155 H
PKE
IND
0000 H 0000 H 03E8 H
PWE
high
PWE
low
Illustration 11.15 Response from Slave-to-Master
3E8 hex corresponds to 1000 decimal. The conversion
index for
parameter 3-41 Ramp 1 Ramp Up Time
is -2.
Parameter 3-41 Ramp 1 Ramp Up Time
is of the type
Unsigned 32
.
11.7 RS485: Modbus RTU Overview
11.7.1 Assumptions
Danfoss assumes that the installed controller supports the
interfaces in this manual, and strictly observes all
requirements and limitations stipulated in the controller
and drive.
11.7.2 Prerequisite Knowledge
The Modbus RTU (Remote Terminal Unit) is designed to
communicate with any controller that supports the
interfaces defined in this manual. It is assumed that the
reader has full knowledge of the capabilities and
limitations of the controller.
11.7.3 Modbus RTU Overview
Regardless of the type of physical communication
networks, the Modbus RTU Overview describes the process
a controller uses to request access to another device. This
process includes how the Modbus RTU responds to
requests from another device, and how errors are detected
and reported. It also establishes a common format for the
layout and contents of message fields.
During communications over a Modbus RTU network, the
protocol determines:
•
How each controller learns its device address.
•
Recognizes a message addressed to it.
•
Determines which actions to take.
•
Extracts any data or other information contained
in the message.
If a reply is required, the controller constructs the reply
message and sends it.
Controllers communicate using a master-slave technique in
which only 1 device (the master) can initiate transactions
(called queries). The other devices (slaves) respond by
supplying the requested data to the master, or by
responding to the query.
The master can address individual slaves or can initiate a
broadcast message to all slaves. Slaves return a message,
called a response, to queries that are addressed to them
Appendix
Design Guide
MG06K102
Danfoss A/S © 03/2019 All rights reserved.
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11
Summary of Contents for VLT AutomationDrive FC 361
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