Data rates of 100Kbps can be achieved over distances of up to 1200 meters. Transmission speeds of 30-35 Mbps are supported for distances of up to 10 meters. The RS485 interface achieves superior transmission over greater distances and better data rate performance than the RS232 protocol. The distances these signals are carried is greater due to differential signals. The TxD+ and TxD- lines carry transmit data while the RxD+ and RxD- contain the receive data. RS485 pin configuration for DB 25įigure 3 is an RS485 wiring diagram for RS485 pinout DB9 connectors.įigure 4 is a pin diagram for both 25 pin RS485 pinout half duplex and full duplex pinout connectors. Pinout connects to DB9 and DB25 connectors with 2 and 4 contacts.įigure 4. The signal simply alerts the data terminal but does not impact the data transmission between the devices. Ring Indicator (RI) the purpose of this signal is to alert a modem operating a data set that a low frequency has been detected. It indicates that interference-free transmission is possible between the data set and the data terminal.Ĭlear to Send (CTS) sending this signal after a connection between a data terminal and a modem has been established confirms recognition by the data terminal that communications can commence. Request to Send (RTS) positive voltage is necessary for this signal to allow the request to send (RTS) to be performed. System Ground (GND) refers to a physical connection with the ground, a baseline used for measuring voltages in an electrical circuit, or a shared path for returning electrical current.ĭata Set Ready (DSR) in contrast to the DTR signal, this signal notifies a computer or terminal that the modem is operational and capable of receiving data. Transmit Data (TXD) this is the line that actually carries the transmitted data.ĭata Terminal Ready (DTR) this is the signal that shows that a computer is ready for transmission. An example is data received from a modem transferred to a computer. Receive Data (RXD) this line is used for data transmission between two sources. RS485 pinout RS485 signal line definitionsĬarrier Detect (CD) this control signal is used when a modem informs a computer that it has detected a carrier that the computer can use for data transmission. RS485 pinout DB9 connector is shown below:įigure 2. Meaning of RS485 signal lines the control signals.This has led to the RS485’s wide adoption as the communication interface of choice when multiple nodes need to communicate in control or data acquisition applications. In the EIA’s standard series, the RS485 protocol is considered the most versatile, demonstrating good performance on all four criteria. It also covers the technical RS485 specifications This article describes the RS485 pin configuration including diagrams of full and half duplex RS485 connector pinouts.

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