Siemens SIMATIC NET PROFIBUS, Owner'S Manual

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Configuring Networks
3-7
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000
Table 3-5 Examples Illustrating the Configuration Rules
No special conditions if the length of the LAN cable
between two DTEs > 10 m LAN cable > 10 m
> 10 m
S7-400 S7-300
No special conditions if the length of the LAN ca-
bles between two DTEs is greater than the sum of
values of both DTEs.
If a bus terminal or a bus connector has a PG inter-
face, a connected PG connecting cable must be
taken into account when calculating the values.
Bus cable, e.g. 5 m
V = 1.5 + 1.0 + 0.1 = 2.6
5 m > 2.6 m (sum of the values in
meters)
5 m
V = 1.0
V = 1.5
V = 0.1
S7-400
S7-300
Take the values of a group into account if the sum
of the values is greater than the LAN cable bet-
ween the DTEs.
Elements can be close to each other providing the
total value of a group does not exceed 5.
LAN cable e.g. 0.5 m group
V = 1.5 + 1.5
0.5 m < 3 m
⇒
group formed
⇒
sum of the values
≤
5
0.5 m
V = 1.5 V = 1.5
S7-400 S7-400