Hardware Set-Up; Parameter Settings For Modbus Communication; Emc Precautions; Fc Protocol - Danfoss VLT Midi Drive FC 280 Design Manual

RS485 Installation and Set-...
NOTICE
To reduce noise between conductors, use shielded,
twisted-pair cables.
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Illustration 5.2 Network Connection

5.1.3 Hardware Set-up

To terminate the RS485 bus, use the terminator switch on
the main control board of the frequency converter.
The factory setting for the switch is OFF.
5.1.4 Parameter Settings for Modbus
Communication
Parameter Function
Parameter 8-30 Prot Select the application protocol to run for
ocol the RS485 interface.
Parameter 8-31 Add Set the node address.
NOTICE
ress
The address range depends on the
protocol selected in
parameter 8-30 Protocol.
Parameter 8-32 Bau Set the baud rate.
NOTICE
d Rate
The default baud rate depends on the
protocol selected in
parameter 8-30 Protocol.
Parameter 8-33 Pari Set the parity and number of stop bits.
NOTICE
ty / Stop Bits
The default selection depends on the
protocol selected in
parameter 8-30 Protocol.
Parameter 8-35 Min Specify a minimum delay time between
imum Response receiving a request and transmitting a
Delay response. This function is for overcoming
modem turnaround delays.
Parameter 8-36 Ma Specify a maximum delay time between
ximum Response transmitting a request and receiving a
Delay response.
MG07B102
Design Guide
Parameter
Parameter 8-37 Ma
ximum Inter-char
delay
Table 5.2 Modbus Communication Parameter Settings

5.1.5 EMC Precautions

To achieve interference-free operation of the RS485
network, Danfoss recommends the following EMC
precautions.
NOTICE
Observe relevant national and local regulations, for
example regarding protective earth connection. To avoid
coupling of high-frequency noise between the cables,
keep the RS485 communication cable away from motor
and brake resistor cables. Normally, a distance of
200 mm (8 in) is sufficient. Maintain the greatest possible
distance between the cables, especially where cables run
in parallel over long distances. When crossing is
unavoidable, the RS485 cable must cross motor and
brake resistor cables at an angle of 90°.

5.2 FC Protocol

5.2.1 Overview

The FC protocol, also referred to as FC bus or standard bus,
is the Danfoss standard fieldbus. It defines an access
technique according to the master/slave principle for
communications via a fieldbus.
One master and a maximum of 126 slaves can be
connected to the bus. The master selects the individual
slaves via an address character in the telegram. A slave
itself can never transmit without first being requested to
do so, and direct telegram transfer between the individual
slaves is not possible. Communications occur in the half-
duplex mode.
The master function cannot be transferred to another node
(single-master system).
Danfoss A/S © 03/2016 All rights reserved.
Function
If transmission is interrupted, specify a
maximum delay time between 2 received
bytes to ensure timeout.
NOTICE
The default selection depends on the
protocol selected in
parameter 8-30 Protocol.
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