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13.3
Operation
13.3.1
Overview
The SCI can carry out serial communication in two modes: asynchronous mode in which
synchronization is achieved character by character, and clocked synchronous mode in which
synchronization is achieved with clock pulses.
Selection of asynchronous or clocked synchronous mode and the transmission format is made
using SMR as shown in table 13-8. The SCI clock is determined by a combination of the C/A bit
in SMR and the CKE1 and CKE0 bits in SCR, as shown in table 13-9.
Asynchronous Mode
• Data length: Choice of 7 or 8 bits
• Choice of parity addition, multiprocessor bit addition, and addition of 1 or 2 stop bits (the
combination of these parameters determines the transfer format and character length)
• Detection of framing, parity, and overrun errors, and breaks, during reception
• Choice of internal or external clock as SCI clock source
When internal clock is selected:
The SCI operates on the baud rate generator clock and a clock with the same frequency as
the bit rate can be output
When external clock is selected:
A clock with a frequency of 16 times the bit rate must be input (the on-chip baud rate
generator is not used)
Clocked Synchronous Mode
• Transfer format: Fixed 8-bit data
• Detection of overrun errors during reception
• Choice of internal or external clock as SCI clock source
When internal clock is selected:
The SCI operates on the baud rate generator clock and a serial clock is output off-chip
When external clock is selected:
The on-chip baud rate generator is not used, and the SCI operates on the input serial clock
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