RS-232 (Recommended Standard 232) is a standard for serial communication transmission of data between devices. It was introduced by the Electronic Industries Association (EIA) in the 1960s and has since become one of the most commonly used serial communication standards.
Key features of the RS-232 interface standard include:
-
Physical Interface: RS-232 uses a serial communication interface, meaning that data is transmitted one bit at a time over a single communication line. The physical interface typically consists of a DB-9 or DB-25 connector with pins for transmitting (TX), receiving (RX), ground (GND), and control signals.
-
Voltage Levels: RS-232 defines voltage levels for logic 1 and logic 0 signals. A positive voltage (+3 to +15 volts) represents a logic 0, while a negative voltage (-3 to -15 volts) represents a logic 1. These voltage levels allow for reliable long-distance communication (up to 50 feet without additional hardware).
-
Asynchronous Communication: RS-232 supports asynchronous communication, meaning that data is transmitted without the need for a shared clock signal between devices. Instead, the data is accompanied by start and stop bits to synchronize communication.
-
Data Rate: RS-232 supports various data transmission rates (baud rates), typically ranging from 110 bits per second (bps) to 115,200 bps or higher, depending on the implementation and hardware capabilities.
-
Handshaking Signals: RS-232 defines several control signals for handshaking and flow control between devices. These include signals for hardware flow control (RTS/CTS) and software flow control (XON/XOFF), which help regulate the flow of data to prevent data loss or buffer overflow.
-
Error Detection: While RS-232 does not specify error detection or correction mechanisms, it allows for the transmission of parity bits for basic error detection. However, more robust error detection and correction are typically implemented at higher protocol layers.
RS-232 has been widely used for connecting devices such as modems, printers, terminals, and computers to peripherals. However, due to its limitations in terms of distance, speed, and susceptibility to noise, RS-232 has largely been replaced by newer serial communication standards such as USB (Universal Serial Bus), Ethernet, and RS-485 in many applications. Nonetheless, RS-232 remains relevant in certain niche applications and legacy systems.
