10.3.3
Operation
1. Overview
SCI3 can perform serial communication in two modes: asynchronous mode in which
synchronization is provided character by character, and synchronous mode in which
synchronization is provided by clock pulses. The serial mode register (SMR) is used to select
asynchronous or synchronous mode and the data transfer format, as shown in table 10-11.
The clock source for SCI3 is determined by bit COM in SMR and bits CKE1 and CKE0 in SCR3,
as shown in table 10-12.
a. Asynchronous mode
•
•
Choice of 5-, 7-, or 8-bit data length
Choice of parity addition, multiprocessor bit addition, and addition of 1 or 2 stop bits. (The
combination of these parameters determines the data transfer format and the character length.)
•
•
Framing error (FER), parity error (PER), overrun error (OER), and break detection during
reception
Choice of internal or external clock as the clock source
When internal clock is selected: SCI3 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 16 times the bit rate must be input.
(The on-chip baud rate generator is not used.)
b. Synchronous mode
•
•
•
Data transfer format: Fixed 8-bit data length
Overrun error (OER) detection during reception
Choice of internal or external clock as the clock source
When internal clock is selected: SCI3 operates on the baud rate generator clock, and a serial
clock is output.
When external clock is selected: The on-chip baud rate generator is not used, and SCI3
operates on the input serial clock.
290
ETC [ ETC ]
