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ML610471/472/473/Q471/Q472/Q473 User's Manual
Chapter 11 UART
11-12
11.3.2 Baud rate
Baud rates are generated by the baud generator.
The baud rate generator generates a baud rate by counting the clock selected by the baud rate clock selection bits
(U0CK1, U0CK0) of the UART0 mode register 0 (UA0MOD0). The count value of the baud rate generator can be set by
writing it in the UART0 baud rate register H or L (UA0BRTH, UA0BRTL). The maximum count is 4096.
The setting values of UA0BRTH and UA0BRTL are expressed by the following equation.
Clock frequency (Hz)
UA0BRTH, L
＝
Baud rate (bps)
—
１
Table 11-2 lists the count values for typical baud rates.
Table 11-2 Count Values for Typical Baud Rates
Baud rate generator
Clock selection
Baud rate generator counter value
Baud rate
Baud rate
Clock
U0CK1 U0CK0
Count
value
Period of
one bit
UA0BRTH UA0BRTL
Error
[%]
1200bps 32.768kHz 0 0 27 Approximately 824us 00H 1AH 1.1
32.768kHz 0 0 14 Approximately 427us 00H 0DH -2.5
2400bps
65.536kHz 0 1 27 Approximately 412us 00H 1AH 1.1
32.768kHz 0 0 7 Approximately 214us 00H 06H -2.5
65.536kHz 0 1 14 Approximately 214us 00H 0DH -2.5
4800bps
500kHz 1
＊
104 Approximately 208us 00H 67H 0.2
65.536kHz 0 1 7 Approximately 107us 00H 06H -2.5
9600bps
500kHz
1
＊
52 Approximately 104us 00H 33H 0.2
19200bps
500kHz
1
＊
26 Approximately 52us 00H 1BH 0.2
38400bps
500kHz
1
＊
13 Approximately 26us 00H 0CH 0.2
Note:
When using 65.536KHz (LSCLK X 2) for the baud rate generator input clock, enable the operation of the low-speed
double clock by setting bit 2 (ENMLT) of the frequency control register 1 (FCON1) to “1”.
When the baud rate clock generator input clock selection is set to 500kHz, an error of 500kHz±25% may occur. To
set the baud rate with accuracy, set the baud rate generator counter value by referring to the frequency measurement
modes for Timers 2 and 3 (Sections 9.3.3).