Frequency Converter Hardware Setup; Frequency Converter Parameter Settings For Modbus Communication; Emc Precautions; Fc Protocol Overview - Danfoss VLT HVAC Drive FC 102 Design Manual

Installation and Set-up

7.1.2 Frequency Converter Hardware Setup

Use the terminator dip switch on the main control board
of the frequency converter to terminate the RS-485 bus.
Illustration 7.3 Terminator Switch Factory Setting
7 7
The factory setting for the dip switch is OFF.
7.1.3 Frequency Converter Parameter
Settings for Modbus Communication
The following parameters apply to the RS-485 interface
(FC-port):
Parameter
8-30 Protocol
8-31 Address
8-32 Baud Rate
8-33 Parity / Stop
Bits
8-35 Minimum
Response Delay
8-36 Maximum
Response Delay
8-37 Maximum
Inter-Char Delay
Table 7.2 RS-485 Parameters
170
Design Guide
ON
1 2
Function
Select the application protocol to run on
the RS-485 interface
Set the node address. Note: The address
range depends on the protocol selected in
8-30 Protocol
Set the baud rate. Note: The default baud
rate depends on the protocol selected in
8-30 Protocol
Set the parity and number of stop bits.
Note: The default selection depends on the
protocol selected in 8-30 Protocol
Specify a minimum delay time between
receiving a request and transmitting a
response. This can be used for overcoming
modem turnaround delays
Specify a maximum delay time between
transmitting a request and receiving a
response
Specify a maximum delay time between
two received bytes to ensure time-out if
transmission is interrupted
Danfoss A/S © Rev. 05/2014 All rights reserved.

7.1.4 EMC Precautions

The following EMC precautions are recommended in order
to achieve interference-free operation of the RS-485
network.
Observe relevant national and local regulations regarding
protective ground connection. Keep the RS-485 communi-
cation cable away from motor and brake resistor cables to
avoid coupling of high frequency noise from one cable to
another. Normally a distance of 200 mm (8 inches) is
sufficient, but it is best to keep the greatest possible
distance between the cables, especially where cables run
in parallel over long distances. When crossing is
unavoidable, the RS-485 cable must cross motor and brake
resistor cables at a 90° angle.
Min.200mm
90° crossing
Illustration 7.4 Crossing Cables

7.2 FC Protocol 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 serial bus.
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 message transfer between the individual
slaves is not possible. Communications occur in the half-
duplex mode.
MG16C202