Specifications

34 Chapter 7 EIA-485 asynchronous interface
Digi EIA-485 connector wiring
Two wires (one twisted pair) are required for each signal, a positive lead
(“+”), and a negative lead (“-”). The “+” leads at one end of the cable must
be connected to the “+” leads at the other end, and the “-” leads at one end
must be connected to the “-” leads at the other end.
Caution: Incorrect wiring could result in damage to the connected devices.
The following tables show the pin configurations for the EIA-485 versions
of Digi DB-9 and RJ-45 10-pin connectors.
RJ-45 pinouts
DB-9 pinouts
RJ-45 pin
485 half
duplex
485 full
duplex
Signal description
1 TxD- TxD- Transmitted Data (-)
2 RxD- RxD- Received Data (-)
3 n/a RTS+ Request To Send (+)
4 GND GND Chassis Ground
5 TxD+ TxD+ Transmitted Data (+)
6 RxD+ RxD+ Received Data (+)
7 SG SG Signal Ground
8 n/a CTS+ Clear To Send (+)
9 n/a RTS- Request To Send (-)
10 n/a CTS- Clear To Send (-)
DB-9
pin
Screw
terminal
485 half duplex
485 full
duplex
Signal description
1 9 Not used CTS- Clear To Send (-)
2 6 RxD+ RxD+ Received Data (+)
3 3 TxD+ TxD+ Transmitted Data (+)
4 2 Not used RTS- Request To Send (-)
5 5 GND GND Chassis Ground
6 7 RxD- RxD- Received Data (-)
7 1 Not used RTS+ Request To Send (+)
8 8 Not used CTS+ Clear To Send (+)
9 4 TxD- TxD- Transmitted Data (-)