LAPIS Semiconductor ML610421, Руководство пользователя, Страница: 207 / 437

ML610Q421/ML610Q422/ML610421 User’s Manual
Chapter 14 UART
14 – 12
14.3.2 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.
UA0BRTH, L =
Clock frequency (Hz)
–1
Baud rate (bps)
Table 14-2 lists the count values for typical baud rates.
Table 14-2 Count Values for Typical Baud Rates
Baud rate
Baud rate generator
clock selection
Count value of the baud rate generator
Baud rate
clock
U0CK1 U0CK0 Count value Period of 1 bit UA0BRTH UA0BRTL
1200 bps 32.768 kHz 0 0 27 Approx. 824
µ
s 00H 1AH
2400 bps 65.536 kHz 0 1 27 Approx. 412
µ
s 00H 1AH
4800 bps 4.096 MHz 1 * 853 Approx. 208
µ
s 03H 054H
9600 bps 4.096 MHz 1 * 427 Approx. 104
µ
s 01H 0AAH
19200 bps 4.096 MHz 1 * 213 Approx. 52
µ
s 00H 0D4H
38400 bps 4.096 MHz 1 * 107 Approx. 26
µ
s 00H 06AH
57600 bps 4.096 MHz 1 * 71 Approx. 17.3
µ
s 00H 046H
115200 bps 4.096 MHz 1 * 36 Approx. 8.8
µ
s 00H 023H
Note:
When UA0BRTH or UA0BRTL is set to a value equal to less than “0007H”, the value set is read from UA0BRTH or
UA0BRTL but the value of the baud rate clock counter is the same as the value when UA0BRTH or UA0BRTL is set
to “0008H”.
When specifying 65.536 kHz (LSCLK
×
2) for the clock, enable the operation of the 2
×
low-speed clock by setting bit 2
(ENMLT) of the frequency control register 1 (FCON1) to “1”.
Compensating tolerant of RC oscillation 500kHz with Timer can support errors of +/- 2% or less at 9600bps. See
Section 10.3.2., “Frequency measurement mode”.