4-6
C7-621 / C7-621 AS-i Control Systems
C79000-G7076-C621-01
If you install the nodes of a subnet or an S7-300 without grounding, only an
ungrounded programming device can be connected to the subnet or to the
S7-300.
You want to use ungrounded nodes. If the MPI is grounded on the PG, you
must include an RS 485 repeater between the nodes and the PG. The
ungrounded nodes must be connected to bus segment 2 if the PG is connected
to bus segment 1 (terminals A1 B1) or the programming device/OP interface
(see Chapter 7 in the reference manual Module Data).
Figure 4-4 shows the RS 485 repeater as an interface between a grounded and
an ungrounded node in an MPI subnet.
C7
Bus segment 2
signals ungrounded
PG
Bus segment 1
signals grounded
Figure 4-4 PG Connected to an Ungrounded S7-300
Attaching a
Programming
Device to an
Ungrounded Node
Connecting a
Grounded
Programming
Device to the MPI
Connecting a Programming Device / PC to a C7
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