Oversampling By 8 - ST STM32F405 Reference Manual

RM0090
Table 142. Error calculation for programmed baud rates at f
Baud rate
S.No Desired
15. 7.168 MBps
16. 7.3728 MBps N.A
17. 9 MBps
18. 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 143. 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. 38.4 KBps
5. 57.6 KBps
6. 115.2 KBps
7. 230.4 KBps
8. 460.8 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
Universal synchronous asynchronous receiver transmitter (USART)
oversampling by 16
Oversampling by 16 (OVER8=0)
f = 42 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
N.A N.A
N.A
N.A N.A
N.A N.A

oversampling by 8

Oversampling by 8 (OVER8=1)
f = 42 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
2.4 KBps 2187.5
9.6 KBps 546.875
19.195 KBps 273.5
38.391 KBps 136.75
57.613 KBps 91.125
115.068 KBps 45.625
230.769 KBps 22.75
461.538 KBps 11.375
913.043 KBps 5.75
1.826 MBps 2.875
1.826 MBps 2.875
3.5 MBps 1.5
3.82 MBps 1.375
N.A N.A
N.A N.A
(1)(2)
(continued)
% Error =
(Calculated -
Desired)B.Rate
/Desired B.Rate
N.A
N.A
N.A
N.A
PCLK
(1)(2)
Value
programmed
in the baud
rate register
0
0
0.02
0.02
0.02
0.11
0.11
0.16
0.93
1.9
0.93
2.34
3.57
N.A
N.A
RM0090 Rev 18
= 42 MHz or f
PCLK PCLK
f = 84 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
N.A N.A
N.A N.A
N.A N.A
N.A N.A
= 42 MHz or f
PCLK
f = 84 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
2.4 KBps NA
9.6 KBps 1093.75
19.2 KBps 546.875
38.391 KBps 273.5
57.613 KBps 182.25
115.226 KBps 91.125
230.137 KBps 45.625
461.538 KBps 22.75
923.076 KBps 11.375
1.787Mbps 5.875
1.826 MBps 5.75
3.652 MBps 2.875
3.652 MBps 2.875
7 MBps 1.5
7.636 MBps 1.375
= 84 Hz,
%
Error
N.A
N.A
N.A
N.A
= 84 MHz,
%
Error
0
0
0
0.02
0.02
0.02
0.11
0.16
0.93
0.27
0.93
1.9
0.93
2.34
3.57
987/1749
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