Renesas Hitachi H8S/2191, Hardware Manual

Page: 493 / 1065

Rev. 2.0, 11/00, page 466 of 1037
23.3 Operation
23.3.1 Overview
The SCI1 can carry out serial communication in two modes: asynchronous mode in which
synchronization is achieved character by character, and synchronous mode in which
synchronization is achieved with clock pulses.
Selection of asynchronous or synchronous mode and the transmission format is made using
SMR1 as shown in table 23.8. The SCI1 clock is determined by a combination of the C/
$ bit in
SMR1 and the CKE1 and CKE0 bits in SCR1, as shown in table 23.9.
(1) 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 SCI1 clock source
— When internal clock is selected:
The SCI1 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 built-in baud rate
generator is not used)
(2) Clock Synchronous Mode
•
Transfer format: Fixed 8-bit data
•
Detection of overrun errors during reception
•
Choice of internal or external clock as SCI1 clock source
— When internal clock is selected:
The SCI1 operates on the baud rate generator clock and a serial clock is output off-
chip
— When external clock is selected:
The built-in baud rate generator is not used, and the SCI1 operates on the input serial
clock