![]() ![]() The current revision is TIA-232-F Interface Between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange, issued in 1997. Revision C was issued in a document dated August 1969. The standard continued to be revised and updated by the Electronic Industries Alliance and since 1988 by the Telecommunications Industry Association (TIA). ![]() The standard has been renamed several times during its history as the sponsoring organization changed its name, and has been variously known as EIA RS-232, EIA 232, and most recently as TIA 232. While it has largely been supplanted by other interface standards, such as USB, in computer products, it is still used to connect older designs of peripherals, industrial equipment (such as based on PLCs), and console ports, and special purpose equipment such as a cash drawer for a cash register. It remained in widespread use into the late 1990s. For many years, an RS-232-compatible port was a standard feature for serial communications, such as modem connections, on many computers. Later personal computers (and other devices) started to make use of the standard so that they could connect to existing equipment. Some manufacturers therefore built transmitters that supplied +5V and -5V and labeled them as "RS-232 compatible." A common deviation from the standard was to drive the signals at a reduced voltage: the standard requires the transmitter to use +12V and -12V, but requires the receiver to distinguish voltages as low as +3V and -3V. The lack of adherence to the standards produced a thriving industry of breakout boxes, patch boxes, test equipment, books, and other aids for the connection of disparate equipment. Common problems were non-standard pin assignment of circuits on connectors, and incorrect or missing control signals. ![]() Since application to devices such as computers, printers, test instruments, and so on was not considered by the standard, designers implementing an RS-232 compatible interface on their equipment often interpreted the requirements idiosyncratically. The C revision of the standard was issued in 1969 in part to accommodate the electrical characteristics of these devices. When electronic terminals (smart and dumb) began to be used, they were often designed to be interchangeable with teletypes, and so supported RS-232. The original DTEs were electromechanical teletypewriters and the original DCEs were (usually) modems. Details of voltage levels, slew rate, and short-circuit behavior are typically controlled by a line-driver that converts from the UART's logic levels to RS-232 compatible signal levels, and a receiver that converts from RS-232 compatible signal levels to the UART's logic levels. Many modern devices support speeds of 115,200 bit/s and aboveĭetails of character format and transmission bit rate are controlled by the serial port hardware, often a single integrated circuit called a UART that converts data from parallel to asynchronous start-stop serial form. ![]() bit rates for transmission, although the standard says it is intended for bit rates lower than 20,000 bits per second.protocols for error detection or algorithms for data compression.the framing of characters in the data stream (bits per character, start/stop bits, parity).character encoding (for example, ASCII, Baudot code or EBCDIC).The standard does not define such elements as Standard subsets of interface circuits for selected telecom applications.Functions of each circuit in the interface connector.Interface mechanical characteristics, pluggable connectors and pin identification.Electrical signal characteristics such as voltage levels, signaling rate, timing and slew-rate of signals, voltage withstand level, short-circuit behavior, and maximum load capacitance.The Electronics Industries Association (EIA) standard RS-232-C as of 1969 defines: It is commonly used in computer serial ports. In telecommunications, RS-232 (Recommended Standard 232) is a standard for serial binary data signals connecting between a DTE (Data Terminal Equipment) and a DCE (Data Circuit-terminating Equipment). ![]()
0 Comments
Leave a Reply. |