Siemens Simatic S7-200 System Manual page 232

S7-200 Programmable Controller System Manual
Biasing and Terminating the Network Cable
Siemens provides two types of network connectors that you can use to easily connect multiple devices to
a network: a standard network connector (see Table 7-6 for the pin assignments), and a connector that
includes a programming port, which allows you to connect a programming station or an HMI device to the
network without disturbing any existing network connections. The programming port connector passes all
signals (including the power pins) from the S7-200 through to the programming port, which is especially
useful for connecting devices that draw power from the S7-200 (such as a TD 200).
Both connectors have two sets of terminal screws to allow you to attach the incoming and outgoing
network cables. Both connectors also have switches to bias and terminate the network selectively.
Figure 7-19 shows typical biasing and termination for the cable connectors.
Cable must be terminated
and biased at both ends.
7
Switch position = On:
Terminated and biased
TxD/RxD +
TxD/RxD -
Cable shield
Figure 7-19
Choosing the CP Card or PC/PPI Cable for Your Network
As shown in Table 7-7, STEP 7–Micro/WIN supports several CP cards that allow the programming station
(your computer or SIMATIC programming device) to act as a network master.
The CP cards contain dedicated hardware to assist the programming station in managing a multi-master
network and can support different protocols at several baud rates. The PC/PPI cable also allows you to
enable multiple masters.
Each CP card provides a single RS-485 port for connection to the network. The CP 5511 PCMCIA card
has an adapter that provides the 9-pin D port. You connect one end of the cable to the RS-485 port of the
card and connect the other end to a programming port connector on your network.
If you are using a CP card with PPI communications: STEP 7–Micro/WIN does not support two different
applications running on the same CP card at the same time. You must close the other application before
connecting STEP 7–Micro/WIN to the network through the CP card.
Caution
Using a non-isolated RS-485-to-RS-232 converter can damage the RS-232 port of your computer.
The Siemens PC/PPI cable (order number 6ES7 901–3BF21–0XA0) provides electrical isolation
between the RS-485 port on the S7-200 CPU and the RS-232 port that connects to your computer. If
you do not use the Siemens PC/PPI cable, you must provide isolation for the RS-232 port of your
computer.
220
Switch position = On
Terminated and biased
On
A B A B
Ô
Ô
Bare shielding: approximately 12 mm (1/2 in.) must contact the metal guides of all locations.
Pin #
6
390 Ω
B
3
Network
220 Ω
A
connector
8
390 Ω
5
1
Bias and Termination of the Network Cable
Switch position = Off Switch position = On
No termination or bias Terminated and biased
Off
A B A B A B A B
Ô Ô Ô
Ô Ô Ô
Switch position = Off:
No termination or bias TxD/RxD +
TxD/RxD -
Cable shield
TxD/RxD +
TxD/RxD -
Cable shield
On
B
Pin #
A
6
B
3
A
8
5
1