Danfoss Metasys N2 Design Guide

14.3.1 EMC Precautions
To achieve interference-free operation of the RS485
network, the following EMC precautions are recommended.
Relevant national and local regulations, regarding
protective ground connection, for example, must be
observed. The RS485 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 in) is sucient.
However, in situations where cables run in parallel over
long distances, keeping the greatest possible distance
between cables is recommended. When crossing is
unavoidable, the RS485 cable must cross motor and brake
resistor cables at an angle of 90°.
(2000 mm (78.7 in))
Minimum
90° crossing
e30ba080.12
Fieldbus cable
Illustration 14.4 EMC Precautions
14.4
RS485: FC Protocol Overview
14.4.1 FC Protocol Overview
The FC protocol, also referred to as FC bus or standard bus,
is the Danfoss standard eldbus. It denes an access
technique according to the master/slave principle for
communications via a eld 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 rst 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 RS485, thus utilizing the RS485 port
built into the drive. The FC protocol supports dierent
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.
14.4.2 Drive Set-up
Set the following parameters to enable the FC protocol for
the drive.
Parameter number Setting
Parameter 8-30 Protocol FC
Parameter 8-31 Address 1–126
Parameter 8-32 FC Port
Baud Rate
2400–115200
Parameter 8-33 Parity /
Stop Bits
Even parity, 1 stop bit (default)
Table 14.3 FC Protocol Parameters
14.5
RS485: FC Protocol Telegram Structure
14.5.1 Content of a Character (Byte)
Each character transferred begins with a start bit. Then 8
data bits are transferred, each corresponding to a byte.
Each character is secured via a parity bit. This bit is set at
1" when it reaches parity. Parity is when there is an equal
number of 1 characters in the 8 data bits and the parity bit
in total. A stop bit completes a character, thus consisting
of 11 bits in all.
0 1 32 4 5 6 7
195NA036.10
Start
bit
Even Stop
Parity bit
Illustration 14.5 Character (Byte)
14.5.2 Telegram Structure
Each telegram has the following structure:
•
Start character (STX)=02 hex.
•
A byte denoting the telegram length (LGE).
•
A byte denoting the drive address (ADR).
Appendix Design Guide
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Danfoss Metasys N2 Specifications

General

Brand	Danfoss
Model	Metasys N2
Category	DC Drives
Language	English