Rs422 Operation; Figure 1 - Rs422 Wiring - GridConnect NET485 Manual

Overview

1.2.2 RS422 Operation

The NET485 can handle both RS485 and RS422 communications. This is done by connecting the processor
(CPU) to a pair of RS485 transceivers. The following schematic demonstrates how the circuit is wired for
RS422.
For RS422 mode, use the four signals produced by the two transceivers plus a signal ground as shown in
Figure 1 – RS422 Wiring
3.3V
2
3
Vcc
4
4
TX
1
CPU
3.3V
2
R13
6
CP0
10K
3
3.3V
4
5 1
RX
2
3 2
GND
1
J2
1
TXDA
TXDB
RXDA
RXDB
SGND
Figure 1 – RS422 Wiring
The transmit section of the CPU is labeled TX on pin 4. The receive section of the CPU is labeled RX on
pin 5. Note that the CP0
connected to both transceivers. The transmit section is enabled with a High signal on pin 3, U2 and the
receive section is enabled with a Low signal on pin 2, U4.
There is a jumper option J2 that permits RS485/RS422 Half Duplex or RS422 Full Duplex. With the jumper
in the factory set position between pins 2 and 3, the unit is set for RS485/RS422 Half Duplex.
1-4
3.3V
8
Vcc
DE
D
DI
6
R
7
RO
RE
GND
5
3.3V
8
Vcc
DE
D
DI
6
R
7
RO
RE
GND
5
pin on the CPU pin 6, which is configured to control the level of RS485_TXEN, is
RS422
Half-Duplex
Mode
TXDA (Pin 7)
TXDB (Pin 6)
RXDA (Pin 5)
RXDB (Pin 4)
SGND (Pin 3)
NET485 User Guide