Operation of the UART
This section describes the UART operation.
■ Operating Modes of the UART
The UART has the operating modes shown in Table 14.1-2 . Set a value in the SMR and SCR registers to
switch mode. Table 14.1-2 lists the UART operating modes.
Table 14.1-2 UART Operating Modes
The stop bit length in asynchronous (start-stop synchronization) mode can be specified only for a send
operation. The stop bit length is always one bit for a receive operation. Since operation is possible only
in the above modes, do not make any other setting.
■ Selecting a Clock for the UART
a) Internal timer
If you select the U-TIMER by setting CS0 to "0", the baud rate is determined according to the reload
value set for the U-TIMER. At this time, you can calculate the baud rate as follows:
Asynchronous (start-stop synchronization): Φ/(8 x β)
CLK synchronous: Φ/β
Φ: Peripheral machine clock frequency
β: Cycle defined for the U-TIMER (2n+2 or 2n+3; n is the reload value.)
In asynchronous (start-stop synchronization) mode, data can be transferred in the range from
+1% of the specified baud rate.
b) External clock
If you select an external clock by setting CS0 to "1", the baud rate is as follows (the frequency of the
external clock is assumed to be f):
Asynchronous (start-stop synchronization): f/8
CLK synchronous: f
However, that the maximum value for f is 3.125 MHz.
CLK synchronous mode
Stop bit length