Building Your Network; General Guidelines - Siemens SIMATIC S7 System Manual

Communication
8.6 RS485
Note
When you press the "Find CPUs" button, the EM DP01 PROFIBUS DP module autobauds
and displays in the "Found CPUs " folder at 9.6 Kbps. If you want to communicate through a
DP01 modules at a higher baud rate, you must press the "Add CPU" button and add the EM
DP01 module using the module's network address and specify a baud rate such as 187.5
Kbps.
You must power cycle the DP01 module to connect at the new baud rate.
8.6.5

Building your network

8.6.5.1

General guidelines

Always install appropriate surge suppression devices for any wiring that could be subject to
lightning surges.
Avoid placing low-voltage signal wires and communication cables in the same wire tray with
AC wires and high-energy, rapidly switched DC wires. Always route wires in pairs, with the
neutral or common wire paired with the hot or signal-carrying wire.
The communication port of the S7-200 SMART CPU is not isolated. Consider using an
RS485 repeater to provide isolation for your network.
NOTICE
Avoiding unwanted current flow
Interconnecting equipment with different reference potentials can cause unwanted currents
to flow through the interconnecting cable.
These unwanted currents can cause communications errors or can damage equipment.
Be sure all equipment that you are about to connect with a communications cable either
shares a common circuit reference or is isolated to prevent unwanted current flows.
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System Manual, V2.3, 07/2017, A5E03822230-AF
S7-200 SMART