from
The Free On-line Dictionary of Computing (8 July 2008)
stop bit
In serial communications, where each bit of the message is
transmitted in sequence, stop bits are extra "1" bits which
follow the data and any {parity} bit. They mark the end of a
unit of transmission (normally a byte or character).
For example, characters on an {EIA-232} {serial line} may have
one or two stop bits added. Some {UARTs} even allow for 1.5
stop bits but one is probably the most commonly used. A
serial connection may be described as, for example, "8N1"
which means eight data bits, no {parity} and one stop bit.
(1995-01-24)