RS-232, RS-422, RS-485

RS-232

Almost each PC with one serial interface (RS232C). This PC serial port interface is single ended (connects only two devices with each other), the data rate is less than 20 kbps. It's a voltage loop serial interface with full-duplex communication represented by voltage levels with respect to system ground. A common ground between the PC and the associated device is necessary.

DB-9 PinNameDirDescription9 pin D-SUB male connector at the computer
1CD

Carrier Detect
2RXD

Receive Data
3TXD

Transmit Data
4DTR

Data Terminal Ready
5GND

System Ground
6DSR

Data Set Ready
7RTS

Request to Send
8CTS

Clear to Send
9RI

Ring Indicator

RS-422 (9 pin) connector pinout

PinSignal9 pin D-SUB female connector
1Tx-
Pin out define by Manufacturers
2Tx+
3Rx+
4Rx-

RS-485 (9 pin) connector pinout

PinSignal9 pin D-SUB female connector
1Data-
Pin out define by Manufacturers
2Data+