B&B Electronics MESR424T_D-MT_D-SC - Manual - Manual (Page 71)

10. Glossary
Terminal Block Serial Port Pinouts
Terminal RS-232 Direction (RS-232) RS-422 RS-485
A RTS Output TDA (-) Data A (-)
B TD Output TDB (+) Data B (+)
C CTS Input RDA (-) ---
D RD Input RDB (+) ---
E GND --- GND GND
In the RS-422 mode, TX lines are outputs and RX lines are inputs. Connect the Modbus
gateway TXB(+) line to the RXB(+) line of the Modbus network, and the Modbus
gateway TXA(-) to the RXA(-) of the Modbus network.
Ground is signal ground and provides a common mode reference for the RS-422 Receiver
and Transmitters.