5 Installation and Connection
(continued)
5-12
C232-302-401/402/403/404-603 / C232/EN M/A23
A communication link consisting of a communication master and several slaves can be
established via the RS 485 interface. The communication master can be a control
station, for example. The devices connected to the communication master, such as the
C232, are the communication slaves.
The RS 485 interface of the C232 is designed electrically to permit full-duplex operation
through a 4-wire connection. However, communication through the RS 485 interface is
always in the half-duplex mode of operation. The following connection instructions must
always be followed:
Always use twisted-pair shielded cables only, the kind used for telecommunications
systems.
At least one symmetrically twisted core pair will be required.
Strip cable cores and cable shield right at the connection point and connect properly
in accordance with specifications.
Ground all shields at both ends (large-area grounding).
Ground free (unshielded) cores at one end only.
As another option, a 2-wire or 4-wire connection is also possible. For the 4-wire
connection, a cable with two symmetrically twisted core pairs is required. Figure 5-8
shows the 2-wire connection and Figure 5-9 the 4-wire connection, as illustrated for
channel 2 of the communication module. If channel 1 of the communication module is
designed as an RS 485 interface, then the same arrangement would apply.
2-wire connection
:
Transmitter and receiver must be bridged in all devices that have a full-duplex interface
as part of their electrical system – like the C232, for example. In the two devices that
form the physical ends of the line, the pair of leads must be terminated by a
200-to-220-Ω resistor. In most AREVA devices, and also in the C232, a 220-Ω resistor
is integrated into the RS 485 interface and can be connected by means of a wire jumper.
An external resistor is therefore not necessary.
4-wire connection
:
Transmitter and receiver must be bridged in the device that forms one physical end of
the line. The receivers of the slaves that have a full-duplex interface as part of their
electrial system (like the C232, for example) are connected to the transmitter of the
communication master, and the transmitters of the slaves are connected to the receiver
of the master. Devices that only have a half-duplex interface are connected to the
transmitter of the communication master. In the last physical participant (master or
slave) of the communication link, the transmitter and receiver must each be terminated
by a 200-to-220-Ω resistor. In most AREVA devices, and also in the C232, a
220-Ω resistor is integrated into the RS 485 interface and can be connected by means of
a wire jumper. An external resistor is therefore not necessary. The second resistor must
be connected to the device externally (see Chapter 13 for the resistor Order No.).
To Next Page
Loading...