ST STM32F412 Reference Manual page 781

RM0402 Universal synchronous receiver transmitter (USART) /universal asynchronous receiver
Table 147. Error calculation for programmed baud rates at f
Baud rate
S.No Desired
15 7.168 MBps
16 7.3728 MBps
18 9 MBps
20 10.5 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 148. Error calculation for programmed baud rates at f
Baud rate
S.No Desired
1 9.600 KBps
2 19.200 KBps
3 38.400 KBps
4 57.600 KBps
5 115.200 KBps
6 230.400 KBps
7 460.800 KBps
8 921.600 KBps
9 3.125 MBps
10 4.000 MBps
11 6.250 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.
oversampling by 8
Oversampling by 8 (OVER8=1)
f = 42 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
NA NA
NA NA
NA NA
NA NA
oversampling by 16
Oversampling by 16 (OVER16=1)
f = 100 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
9.601 KBps 651
19.201 KBps 325
38.402 KBps 162.75
57.603 KBps 108.5
115.207 KBps 54.25
230.414 KBps 27.125
460.829 KBps 13.5625
925.925 KBps 6.75
3.125 MBps 2
4.000 MBps 1.5625
6.250 MBps 1
PCLK
(1)(2)
(continued)
% Error =
(Calculated -
Desired)B.Rate
/Desired B.Rate
NA
NA
NA
NA
PCLK
(1)(2)
% Error =
(Calculated -
Desired)B.Rate
/Desired B.Rate
0.006
0.006
0.006
0.006
0.006
0.006
0.006
0.470
0
0
0
RM0402 Rev 6
= 42 MHz or f
PCLK
f = 84 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
7 MBps 1.5
7.636 MBps 1.375
9.333 MBps 1.125
10.5 MBps 1
= 100 MHz or f
PCLK
f = 50 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
9.601 KBps 325.5
19.201 KBps 162.75
38.402 KBps 81.375
57.603 KBps 54.25
115.207 KBps 27.125
230.414 KBps 13.5625
462.962 KBps 6.75
925.925 KBps 3.375
3.125 MBps 1
NA NA
NA NA
= 84 MHz,
%
Error
2.34
3.57
3.7
0
= 50 MHz,
%
Error
0.006
0.006
0.006
0.006
0.006
0.006
0.47
0.47
0
NA
NA
781/1163
810