3-8
C7-621 / C7-621 AS-i Control Systems
C79000-G7076-C621-01
3.3 Cable Lengths
The maximum cable length in one segment of an MPI network is 50 m.
These 50 m represent the distance from the first node to the last node on the
segment.
If you require longer cable lengths than permitted in one segment, you must
then use RS 485 repeaters. The maximum possible cable length between RS
485 repeaters corresponds to the cable length of a segment. Remember,
however, that when using these maximum lengths, no further node (remote
segment) can be located between the two RS 485 repeaters. You can connect
up to nine RS 485 repeaters in series.
If you use an RS 485 repeater, remember that this must also be included in
the number of nodes when calculating the number of nodes although it is not
assigned its own MPI number.
Figure 3-5 shows how the cable for an MPI network can be extended using
RS 485 repeaters.
C7
50 m 1000 m 50 m
RS 485
repeater
PROFIBUS LAN cable
(remote segment)
Figure 3-5 Maximum Cable Length Between Two RS 485 Repeaters
Tap lines are cables with which the programming devices or OPs can be
connected to the network for installation or during maintenance. Tap lines
should be kept as short as possible. The number and length of tap lines that
can be used is restricted.
The following table shows the maximum length of tap lines per bus segment:
Table 3-1 Length of the Tap Lines per Segment
Transmission
Rate
Max. Length of
Tap Line per
Number of Nodes with Tap Line
Lengths of ...
Segment
1.5 m or 1.6 m 3 m
187.5 Kbps 75 m 32 25
Segment in an MPI
Network
Longer Cable
Lengths
Tap Lines
Configuring an MPI Network
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