ST STM32F412 Reference Manual page 779

RM0402 Universal synchronous receiver transmitter (USART) /universal asynchronous receiver
Table 145. Error calculation for programmed baud rates at f
Baud rate
S.No Desired
7 460.8 KBps
8 896 KBps
9 921.6 KBps
10 1.792 MBps
11 1.8432 MBps
12 3.584 MBps
13 3.6864 MBps
14 7.168 MBps
15 7.3728 MBps
1. The lower the CPU clock the lower the accuracy for a particular baud rate. The upper limit of the achievable baud rate can
be fixed with these data.
2. Only USART1 and USART6 are clocked with PCLK2. Other USARTs are clocked with PCLK1. Refer to the device
datasheets for the maximum values for PCLK1 and PCLK2.
Table 146. Error calculation for programmed baud rates at f
Baud rate
S.No Desired
1 1.2 KBps
2 2.4 KBps
3 9.6 KBps
4 19.2 KBps 19.195 KBps
5 38.4 KBps 38.391 KBps
6 57.6 KBps 57.613 KBps
7 115.2 KBps 115.068 KBps
8 230.4 KBps 230.769 KBps
9 460.8 KBps 461.538 KBps
oversampling by 8
Oversampling by 8 (OVER8=1)
f = 30 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
461.538 KBps 8.1250
909.091 KBps 4.1250
909.091 KBps 4.1250
1.7647 MBps 2.1250
1.8750 MBps 2.0000
3.7500 MBps 1.0000
3.7500 MBps 1.0000
NA NA
NA NA
oversampling by 16
Oversampling by 16 (OVER8=0)
f = 42 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
1.2 KBps 2187.5
2.4 KBps 1093.75
9.6 KBps 273.4375
136.75
68.375
45.5625
22.8125
11.375
5.6875
PCLK
(1) (2)
(continued)
% Error =
(Calculated -
Desired)B.Rate
/Desired B.Rate
0.16%
1.46%
1.36%
1.52%
1.73%
4.63%
1.73%
NA
NA
(1)(2)
% Error =
(Calculated -
Desired)B.Rate
/Desired B.Rate
0
0
0
0.02
0.02
0.02
0.11
0.16
0.16
RM0402 Rev 6
= 30 MHz or f
PCLK
f =60 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
461.538 KBps 16.2500
895.522 KBps 8.3750
923.077 KBps 8.1250
1.8182 MBps 4.1250
1.8182 MBps 4.1250
3.5294 MBps 2.1250
3.7500 MBps 2.0000
7.5000 MBps 1.0000
7.5000 MBps 1.0000
= 42 MHz or f
PCLK PCLK
f = 84 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
1.2 KBps 4375
2.4 KBps 2187.5
9.6 KBps 546.875
19.2 KBps 273.4375
38.391 KBps 136.75
57.613 KBps 91.125
115.226 KBps 45.5625
230.137 KBps 22.8125
461.538 KBps 11.375
= 60 MHz,
%
Error
0.16%
0.05%
0.16%
1.46%
1.36%
1.52%
1.73%
4.63%
1.73%
= 84 Hz,
%
Error
0
0
0
0
0.02
0.02
0.02
0.11
0.16
779/1163
810