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The RS232 standard is defined by the EIA/TIA (Electronic Industries Alliance / Telecommunications Industry Associations). The standard defines an asynchronous serial data transfer mechanism, as well as the physical and electrical characteristics of the interface.

 

RS232 uses serial bit streams transmitted at a predefined baud rate. The information is separated into characters of 5 to 8 bits lengths. Additional start and stop bits are used for synchronization, and a parity bit may be included to provide a simple error detection mechanism.

 

The electrical interface includes unbalanced line drivers, i.e. all signals are represented by a voltage with reference to a common signal ground. RS232 defines two states for the data signals: mark state (or logical 1) and space state (or logical 0). The range of voltages for representing these states is specified as follows:

 

 

The physical characteristics of the RS232 standard are described in the section RS232 Connectors / Pinout