Modbus RTU over RS-232 uses a DB9 connector for point-to-point serial communication between a master (HMI/SCADA) and a single slave device at up to 115200 baud using 8N1 or 8E1 framing.
| Pin | Name | Function | Type |
|---|---|---|---|
| 1 | DCD | Data carrier detect | I/O |
| 2 | RXD | Receive data | BUS |
| 3 | TXD | Transmit data | BUS |
| 4 | DTR | Data terminal ready | I/O |
| 5 | GND | Signal ground | GND |
| 6 | DSR | Data set ready | I/O |
| 7 | RTS | Request to send | I/O |
| 8 | CTS | Clear to send | I/O |
| 9 | RI | Ring indicator | I/O |
Modbus RTU over RS-232 uses a DB9 connector for point-to-point serial communication between a master (HMI/SCADA) and a single slave device at up to 115200 baud using 8N1 or 8E1 framing.