5.1.2 Network Connection
Connect the frequency converter to the RS485 network
as follows (see also
1.
Connect signal wires to terminal 68 (P+) and
terminal 69 (N-) on the main control board of the
frequency converter.
2.
Connect the cable screen to the cable clamps.
NOTICE
Screened, twisted-pair cables are recommended to
reduce noise between conductors.
61 68 69
N
P
COMM. GND
130BB795.10
Illustration 5.2 Network Connection
5.1.3 Hardware Set-up
Use the terminator switch on the main control board of
the frequency converter to terminate the RS485 bus.
The factory setting for the switch is OFF.
5.1.4 Parameter Settings for Modbus
Communication
Parameter
Function
8-30 Protocol
Select the application protocol to run for
the RS485 interface.
8-31 Address
Set the node address.
NOTICE
The address range depends on the
protocol selected in
8-30 Protocol
.
8-32 Baud Rate
Set the baud rate.
NOTICE
The default baud rate depends on the
protocol selected in
8-30 Protocol
.
8-33 Parity / Stop
Bits
Set the parity and number of stop bits.
NOTICE
The default selection depends on the
protocol selected in
8-30 Protocol
.
8-35 Minimum
Response Delay
Specify a minimum delay time between
receiving a request and transmitting a
response. This function is for overcoming
modem turnaround delays.
Parameter
Function
8-36 Maximum
Response Delay
Specify a maximum delay time between
transmitting a request and receiving a
response.
8-37 Maximum
Inter-char delay
If transmission is interrupted, specify a
maximum delay time between 2 received
bytes to ensure time-out.
NOTICE
The default selection depends on the
protocol selected in
8-30 Protocol
.
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 inches) 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-follower principle for
communications via a serial bus.
One master and a maximum of 126 followers can be
connected to the bus. The master selects the individual
followers via an address character in the telegram. A
follower itself can never transmit without first being
requested to do so, and direct message transfer between
the individual followers is not possible. Communications
occur in the half-duplex mode.
The master function cannot be transferred to another node
(single-master system).
RS485 Installation and Set-...
Design Guide
MG06B402
Danfoss A/S © 09/2014 All rights reserved.
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