FCM 300 / FCD 300 / VLT
®
2800 / DP V1 PROFIBUS
The Profibus
Interface
The Profibus Interface
The total drop cable length for one segment is
limited as stated in the table below.
Drop cable length
Transmission speed
Max. drop cable lenth
per segment [m]
9.6-93.75 kBaud
96
187.5 kBaud
75
500 kBaud
30
1.5 mBaud
10
3-12 MBaud
none
The length statements in the tables above
are valid provided that bus cable with the
following properties is used:
- Impedance:
135 to 165 ohm at a measuring
frequency from 3 to 20 MHz
- Resistance:
< 110 ohm/km
- Capacity:
< 30 pF/m
- Damping:
max. 9 dB over the whole wire
length
- Cross section:
max. 0.34 mm
2
, corresponding
to AWG 22
- Cable type:
twisted in pairs,
1 x 2, or 2 x 2, or 1 x 4 wires
- Screening:
Copper-braided screen or
braided screen and foil screen
It is recommended to use the same cable type in the
entire network to avoid impedance mismatch.
The numbers on the following drawing indicate the
maximum number of stations in each segment. They
are not the station addresses as each station in the
network must have a unique address.
Segment 1
Segment 2
Segment 3
Segment 4
R
t
= termination resistors
■
Cable lengths/ number of nodes
The maximum cable length in one segment is
depending on the transmission speed. The total
cable length includes drop cables if any. A drop
cable is the connection from the main bus cable
to each node if a T-connection is used instead of
connecting the main bus cable directly to the nodes,
see drop cable ength. The table below shows the
maximum allowed cable length and maximum number
of nodes/frequency converters with 1, 2, 3 and 4 bus
segments. Note that a repeater is a node in both of the
two segments it connects. The number of frequency
converters is based on a single master system. If
there are more masters the number of frequency
converters must be reduced correspondingly.
MG.90.A5.02 - VLT is a registered Danfoss trademark
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