Specifications

The factory setting for the dip switch is OFF.
7.1.3 Parameter Settings for Modbus
Communication
The following parameters apply to the RS-485 interface
(FC-port):
Parameter Function
O-30 Protocol
Select the application protocol to run on
the RS-485 interface
O-31 Address
Set the node address. Note: The address
range depends on the protocol selected in
O-30 Protocol
O-32 Drive Port
Baud Rate
Set the baud rate. Note: The default baud
rate depends on the protocol selected in
O-30 Protocol
O-33 Drive Port
Parity
Set the parity and number of stop bits.
Note: The default selection depends on the
protocol selected in O-30 Protocol
O-35 Minimum
Response Delay
Specify a minimum delay time between
receiving a request and transmitting a
response. This can be used for overcoming
modem turnaround delays
O-36 Maximum
Response Delay
Specify a maximum delay time between
transmitting a request and receiving a
response
O-37 Maximum
Inter-Char Delay
Specify a maximum delay time between
two received bytes to ensure time-out if
transmission is interrupted
Table 7.2 RS-485 Parameters
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 earth 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.
Fieldbus cable
Min.200mm
90° crossing
130BA080.11
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.
The master function cannot be transferred to another node
(single-master system).
The physical layer is RS-485, thus utilizing the RS-485 port
built into the frequency converter. The FC protocol
supports different telegram formats:
•
A short format of 8 bytes for process data.
•
A long format of 16 bytes that also includes a
parameter channel.
•
A format used for texts.
Installation and Set-up VLT® HVAC Drive FC 102 Design Guide
MG16C102 - Rev. 2013-08-20 163
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