Emc Precautions; Fc Protocol Overview - Danfoss VLT Micro Drive FC 51 Design Manual

RS-485 Installation and Set...

8.1.4 EMC Precautions

The following EMC precautions are recommended in order
to achieve interference-free operation of the RS-485
network.
Relevant national and local regulations, for example
regarding protective earth connection, must be observed.
The RS-485 communication cable must be kept 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 keeping the
greatest possible distance between the cables is generally
recommended, 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 an
angle of 90 degrees.
Min.200mm
90° crossing
Illustration 8.3
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VLT Micro Drive FC 51 Design Guide
8.1.5 Frequency Converter Parameter
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
Table 8.2

8.2 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
Brake resistor
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).
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Settings for Modbus Communication
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 function is for overcoming
modem turnaround delays.
Specify a maximum delay time between
transmitting a request and receiving a
response.
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