Communication
8.6 RS485
S7-200 SMART
400 System Manual, 09/2015, A5E03822230-AC
The following figure shows a PPI network with multiple masters communicating with multiple
slaves. In this example, the HMI can request data from any CPU slave.
All devices (masters and slaves) have different network addresses. The
S7-200 SMART CPUs are slaves.
Building your network
8.6.4.1
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.
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.
To Next Page
Loading...
