NOTE
The factory setting for the dip switch is OFF.
68
69
N (-)
RS485
RS485
P (+)
175ZA907.10
Terminator Switch Factory Setting
7.1.4 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
noisy cables such as power lines and motor cables to
avoid coupling of high frequency noise from one cable to
another. Normally a distance of 200mm (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 other
power cables at an angle of 90
°
.
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 individual slaves are selected by
the master 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 unit. The FC protocol supports different
telegram formats; a short format of 8 bytes for process
data, and a long format of 16 bytes that also includes a
parameter channel. A third telegram format is used for
texts.
7.2 Network Configuration
7.2.1 VLT AutomationDrive Filter Set-up
Set the following parameters to enable the FC protocol for
the filter.
Parameter Number Setting
FC
8-31 Address
1 - 126
2400 - 115200
8-33 Parity / Stop
Bits
Even parity, 1 stop bit (default)
7.3 FC Protocol Message Framing Structure
7.3.1 Content of a Character (byte)
Each character transferred begins with a start bit. Then 8
data bits are transferred, 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 1s 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
3
2
4
5
6
7
195NA036.10
Start
bit
Even Stop
Parity bit
RS-485 Installation and Set...
VLT Active Filter AAF 00x
84
MG.90.V2.02 - VLT® is a registered Danfoss trademark
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7