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The SCI is a universal asynchronous receiver transmitter (UART), one
of two independent serial I/O subsystems in the MC68HC11E9. It has a
standard non return to zero(NRZ) format (one start, eight or nine
data, and one stop bit). Several baud rates are available. The SCI
transmitter and receiver are independent, but use the same data format
and bit rate.
The serial data format requires the following conditions:
- An idle-line in high state before transmission or reception.
- A start bit, logic zero, transmitted or received, that indicates the start
of each character.
- Data that is transmitted and received least significant bit(LSB) first.
- A stop bit, logic one, used to indicate the end of a frame. (A frame consists of
a start bit, a character of eight or nine data bits, and a stop
bit.)
- A break (defined as the transmission or reception of a logic zero for some
multiple number of frames).
Selection of the word length is controlled by the M bit of SCI control
register SCCR1.
Matanya Elchanani
Wed Dec 18 17:00:21 EST 1996