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Difference between RS-232 and RS-485
RS-232 and RS-485 are two serial communication technologies that are frequently used to transfer data between devices through a serial connection. While both standards are used for serial communication, their properties and applications are quite different.
RS-232, commonly known as EIA-232, is a serial communication standard for data transmission between devices. RS-485 is a serial communication standard for data transmission between devices.
Read this article to find out more about RS-232 and RS-485 and how they are different from each other.
What is RS-232?
RS-232, commonly known as EIA-232, is a serial communication standard for data transmission between devices. It was first used in computer serial ports, modems, and other communication devices in the 1960s. RS-232 communicates over relatively small distances (usually up to 50 feet) at relatively moderate speeds (up to 115.2 kbps) using a single-ended signal. RS-232 additionally features handshaking signals for controlling data flow between devices.
RS-232 communicates over relatively small distances (usually up to 50 feet) at relatively moderate speeds (up to 115.2 kbps) using a single-ended signal. The RS-232 interface uses a DB-9 or DB-25 connector with nine or twenty-five pins, respectively.
The RS-232 signal is made up of voltage levels that represent binary 1 or 0. A binary 1 is represented by a voltage level of +3 to +15 volts, while a binary 0 is represented by a voltage level of -3 to -15 volts. The RS-232 interface also contains handshaking signals, which are used to control data flow between devices. Request to Send (RTS), Clear to Send (CTS), Data Terminal Ready (DTR), and Data Set Ready (DSR) are examples of these signals.
The RTS and CTS signals control data flow from the transmitting device to the receiving device. The transmitting device raises the RTS signal when it is ready to send data, and the receiving device reacts by raising the CTS signal when it is ready to receive data. The DTR and DSR signals are used to control the device connection. The transmitting device indicates that it is connected and ready to send data by raising the DTR signal, and the receiving device responds by raising the DSR signal to indicate that it is connected and ready to receive data.
What is RS-485?
RS-485 is a serial communication standard for data transmission between devices that is used in industrial and automation applications such as manufacturing plants and process control systems. When compared to RS-232, RS-485 uses a differential signal that allows for communication over larger distances (up to 4,000 feet) at faster speeds (up to 10 Mbps).
The RS-485 interface works on a two-wire bus that supports multi-drop communication. This means that several devices can be connected to a single bus, and each device on the bus can communicate with the others. Half-duplex communication is also supported by the RS-485 interface, which means that data can only be transmitted in one direction at a time.
A transmitting device provides data to one or more receiving devices on the bus in RS-485 communication. Before transmitting data, the transmitting device checks whether or not the bus is idle. If the bus is idle, the device sends a start bit to signal that data transmission has begun. The data bits are transmitted after the start bit, followed by a stop bit to indicate the end of the transmission. The data is then received by the receiving device(s), which responds with an acknowledgment signal.
RS-485 also has a number of additional features that make it more helpful in industrial and automation applications. These features include support for extended cable lengths, resistance to electromagnetic interference, and support for multi-drop communication and the half-duplex communication mode.
Difference between RS-232 and RS-485
The following table highlights the major differences between RS-232 and RS-485 −
Characteristics |
RS-232 |
RS-485 |
|---|---|---|
Signal |
Single-ended |
Differential |
Distance |
Up to 50 feet |
Up to 4,000 feet |
Speed |
Up to 115.2 kbps |
Up to 10 Mbps |
Cable |
It uses a point-to-point cable |
It uses a two-wire bus |
Multi-drop |
It does not support multi-drop communication |
It supports multi-drop communication |
Noise immunity |
Low Noise immunity |
High Noise immunity |
Power Consumption |
Low |
Moderate |
Application |
Point-to-Point Communication |
Multi-drop communication for industrial control systems, building automation, etc., |
Conclusion
In conclusion, RS-232 is often used for short-distance, low-speed communication, whereas RS-485 is typically used for longer-distance, higher-speed communication, particularly in industrial and automation applications.
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