Technically, the designation "RS-232" is obsolete. "RS" stood for "Recommended Standard," a status that changed once it was formally adopted as a standard. However, the term RS-232 remains so pervasive in engineering vernacular that it is often used interchangeably with the official TIA EIA-232 designation.
| Pin No. | Signal Name | Abbreviation | Direction (DTE → DCE) | Description | |---------|-------------|--------------|------------------------|-------------| | 1 | Data Carrier Detect | DCD | ← (DCE to DTE) | Modem indicates carrier detected | | 2 | Receive Data | RxD | ← | Serial data into DTE | | 3 | Transmit Data | TxD | → | Serial data out of DTE | | 4 | Data Terminal Ready | DTR | → | DTE is powered and ready | | 5 | Signal Ground | GND | — | Common reference (0V) | | 6 | Data Set Ready | DSR | ← | DCE is ready (powered) | | 7 | Request to Send | RTS | → | DTE requests permission to transmit | | 8 | Clear to Send | CTS | ← | DCE grants permission to transmit | | 9 | Ring Indicator | RI | ← | DCE detects ringing signal | tia eia-232-f specification
The TIA/EIA-232-F standard defines a 1997-approved physical layer specification for unbalanced, serial communication between Data Terminal Equipment (DTE) and Data Circuit-Terminating Equipment (DCE). It establishes electrical characteristics with a maximum capacitive load of 2,500pF and defines specific, single-ended signal lines for control and data interchange. For more details, visit Texas Instruments AN-216 Summary of Well Known Interface Standards Technically, the designation "RS-232" is obsolete
The most critical aspect of the 232-F specification is the electrical layer. Unlike modern logic-level interfaces (e.g., 3.3V or 5V CMOS), EIA-232-F uses bipolar voltages to ensure long-distance noise immunity (up to 15 meters / 50 feet at 20 kbps). | Pin No