12
© Sealevel Systems, Inc.
2106 Manual | SL9094 8/2022
Electrical Specifications
The 422: utilizes a USB UART. This chip features programmable baud rate, data format, 128-byte
dual port TX buffer, and 384-byte dual port RX buffer. The RS-422 transceiver supports data rates from 300
baud up to 921.6K baud.
Connector Pin Out
RS-422 (DB-9 MALE)
Pin
Signal
Name
Mode
1
RX+
Receive Positive
Input
2
RX-
Receive Negative
Input
3
TX-
Transmit Negative
Output
4
TX+
Transmit Positive
Output
5
GND
Ground
6, 7, 8, 9
NC
No Contact
For two wire (half duplex) RS-485, connect the (+) communication wire to pins 1 and 4. Also connect the
(-) wire to pins 2 and 3. Connect the communication ground to pin 5.
Line Termination & Biasing
The inputs have appropriate biasing to keep them in the proper state and are always present. A 1K ohm
pull-down resistor is connected to RX- and a 1K pull-up resistor is connected to RX+. A 120-ohm terminating
resistor is connected between RX+ and RX-.