Oversampling By 8 - ST STM32F405 Reference Manual

RM0090
Table 140. Error calculation for programmed baud rates at f
Baud rate
S.No Desired
9. 921.6 KBps
10. 1.792 MBps 1.1764 MBps
1.8432
11.
MBps
12. 3.584 MBps NA
3.6864
13.
MBps
14. 7.168 MBps NA
7.3728
15.
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 141. Error calculation for programmed baud rates at f
Baud rate
S.No Desired
1. 2.4 KBps
2. 9.6 KBps
3. 19.2 KBps
4. 57.6 KBps
5. 115.2 KBps
6. 230.4 KBps
7. 460.8 KBps
8. 896 KBps
9. 921.6 KBps
10. 1.792 MBps
Universal synchronous asynchronous receiver transmitter (USART)
oversampling by 16
Oversampling by 16 (OVER8=0)
f = 30 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
909.091 KBps 2.0625
1.0625
1.8750 MBps 1.0000
NA
NA NA
NA
NA NA

oversampling by 8

Oversampling by 8 (OVER8=1)
f = 30 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
2.400 KBps 1562.5000
9.600 KBps 390.6250
19.194 KBps 195.3750
57.582 KBps 65.1250
115.385 KBps 32.5000
230.769 KBps 16.2500
461.538 KBps 8.1250
909.091 KBps 4.1250
909.091 KBps 4.1250
1.7647 MBps 2.1250
(1)(2)
(continued)
% Error =
(Calculated -
Desired)B.Rate
/Desired B.Rate
1.36%
1.52%
1.73%
NA
NA
NA
NA
(1) (2)
% Error =
(Calculated -
Desired)B.Rate
/Desired B.Rate
0.00%
0.00%
0.03%
0.16%
0.16%
0.16%
0.16%
1.46%
1.36%
1.52%
RM0090 Rev 18
= 30 MHz or f
PCLK PCLK
f = 60 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
923.077 KBps 4.0625
1.8182 MBps 2.0625
1.8182 MBps 2.0625
3.2594 MBps 1.0625
3.7500 MBps 1.0000
NA NA
NA NA
= 30 MHz or f
PCLK PCLK
f =60 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
2.400 KBps 3125.0000
9.600 KBps 781.2500
19.200 KBps 390.6250
57.582 KBps 130.2500
115.163 KBps 65.1250
230.769 KBps 32.5000
461.538 KBps 16.2500
895.522 KBps 8.3750
923.077 KBps 8.1250
1.8182 MBps 4.1250
= 60 MHz,
%
Error
0.16%
1.36%
1.52%
1.52%
1.73%
NA
NA
= 60 MHz,
%
Error
0.00%
0.00%
0.00%
0.03%
0.03%
0.16%
0.16%
0.05%
0.16%
1.46%
985/1749
1018