USB to Serial Converters Manual
Version 2.1
Document Reference No.: CP_000032 Clearance No.: CP#022
Copyright © Connective Peripherals Pte Ltd
21
Figure 13 shows an RS-422 full-duplex bus with handshaking signals connected. The ES-U-xxxx-x has
built-in resistors for terminating its RxD +/- and CTS +/- inputs, which can be enabled using jumpers.
The TxD +/- and RTS +/- lines which are outputs from the ES-U-xxxx-x are terminated at the receiver at
the other end of the bus as shown. Twisted pair wires are required for each signal pair.
Figure 13 - RS-422 with Handshaking Signals Connected
5.3
RS-485 Signal Pin-out (Half Duplex)
DB-9 Male connector
Table 18 shows the RS-485 (half duplex) pinout of the DB-9 male connector.
Pin Number
Pin Type
Description
1
Out / In
Data
–
= Transmit / Receive Data, negative polarity
2
Out / In
Data+ = Transmit / Receive Data, positive polarity
5
Ground
GND = Signal ground
Shield
Case Ground
Drain = typically connected to the host PC case
Table 18 - RS-485 Half-Duplex Pin-out for DB-9 Connector
Note:
Other pins have no function in this mode and should be left un-connected.
5-way Terminal Block
Table 19 shows the RS-485 (half duplex) pinout of the 5-way terminal block (only available on some
models).
Pin Number
Pin Type
Description
1
Out / In
Data
–
= Transmit / Receive Data, negative polarity
2
Out / In
Data+ = Transmit / Receive Data, positive polarity
5
Ground
GND = Signal ground
Table 19 - RS-485 Half-Duplex Pin-Out for 5-way Terminal Block
Note:
Other terminals have no function in this mode and should be left un-connected.
RS-422 Device
ES-U-xxxx-x
RxD+
TxD+
RxD-
TxD-
TxD+
RxD+
TxD-
RxD-
GND
GND
CTS+
RTS+
CTS-
RTS-
RTS+
CTS+
RTS-
CTS-
