CPC314
C P C 3 1 4 U s e r M a n u a l
21
© 2 0 2 1 F a s t w e l V e r . 0 0 1
Table 1-3
– Purpose of the pins of RS-422/485 (XP16, XP17) ports
The “GNDS” circuit corresponds to the signal isolated “ground” of the interface, the GNDS circuits
of the different ports are isolated from each other and are not interconnected.
By setting the X4, X5 (COM3) and X6, X7 (COM4) jumpers, the matching circuits are connected to
the signal lines of the RS-422 or RS-485 interfaces and the operating mode is set.
For port operation in the RS-485 mode it is necessary to connect the "TX+" with "RX+" lines and
"TX-" with "RX-" lines.
Attention!
For proper operation of RS-422/485 transmit/receive unit in a multiuser network, use the
appropriate jumpers to install 120 Ohm terminators at the 2 most distant network nodes, as well as
the 680 Ohm biasing resistors (at one or two of the most distant network nodes).
Table 1-4
– Configuration of the COM3 (X4, X5) port
Table 1-5
– Configuration of the COM4 (X6, X7) port
Each port contains lightning protection circuits based on protection elements of TBU series and
TISP series thyristor protection circuits. The port also contains TVS diode-based pulse interference
protection circuits. The diagram of the output stages of the COM3 port is shown below (the COM4
port has a similar circuit design).
5
The position of the switches at the time of delivery is highlighted in bold; if none is highlighted, the switches are not set
at delivery.
6
The position of the switches at the time of delivery is highlighted in bold; if none is highlighted, the switches are not set
at delivery.
COM3-4: B5B-PH-KL (JST)
Pin #
Function (RS-422)
Function (RS-485)
1
TX+
RTxD+
2
TX-
RTxD-
3
RX+
-
4
RX-
-
5
GNDS
GNDS
Jumper
Description
X4[1-2]
5
Biasing resistor is set on the line TX+
X5[1-2]
Biasing resistor is set on the line TX-
X4 and X5
120 Ohm matching resistor is connected to the TX+ /
TX-
Jumper
Description
X6[1-2]
8
Biasing resistor is set on the line
TX+
X7[1-2]
Biasing resistor is set on the line TX-
X6 and X7
120 Ohm matching resistor is connected to the TX+ /
TX-