FC101 Design Guide

NOTICE!
Parameter 4-14 Motor Speed High Limit [Hz] is a single
word, and the parameter command for write in EEPROM
is E. Parameter 4-14 Motor Speed High Limit [Hz] is 19E in
hexadecimal.
The response from the slave to the master is shown in
Figure 7.11.
119E H
PKE
IND
PWE
high
PWE
low
0000 H 0000 H 03E8 H
130BA093.10
Figure 7.11 Response from Master
7.5.2 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
Figure 7.12 Telegram
If the value in parameter 3-41 Ramp 1 Ramp Up Time is
10 s, the response from the slave to the master is shown in
Figure 7.13.
130BA267.10
1155 H
PKE
IND
0000 H 0000 H 03E8 H
PWE
high
PWE
low
Figure 7.13 Response
3E8 hex corresponds to 1000 decimal. The conversion
index for parameter 3-41 Ramp 1 Ramp Up Time is -2, that
is, 0.01.
Parameter 3-41 Ramp 1 Ramp Up Time is of the type
Unsigned 32.
7.6
Modbus RTU Overview
7.6.1 Introduction
Danfoss assumes that the installed controller supports the
interfaces in this document, and strictly observes all
requirements and limitations stipulated in the controller
and frequency converter.
The built-in Modbus RTU (remote terminal unit) is
designed to communicate with any controller that
supports the interfaces dened in this document. It is
assumed that the user has full knowledge of the
capabilities and limitations of the controller.
7.6.2 Overview
Regardless of the type of physical communication
networks, this section describes the process that 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 telegram elds.
During communications over a Modbus RTU network, the
protocol:
•
Determines how each controller learns its device
address.
•
Recognizes a telegram addressed to it.
•
Determines which actions to take.
•
Extracts any data or other information contained
in the telegram.
If a reply is required, the controller constructs the reply
telegram and sends it.
Controllers communicate using a master/slave technique in
which only the master can initiate transactions (called
queries). Slaves respond by supplying the requested data
to the master, or by acting as requested in the query.
The master can address individual slaves, or initiate a
broadcast telegram to all slaves. Slaves return a response
to queries that are addressed to them individually. No
responses are returned to broadcast queries from the
master.
The Modbus RTU protocol establishes the format for the
master query by providing the following information:
•
The device (or broadcast) address.
•
A function code dening the requested action.
•
Any data to be sent.
•
An error-checking eld.
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HVAC Basic Drive FC 101
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