Oversampling By 16; Oversampling By 8 - ST STM32F405 Reference Manual

RM0090
Table 138. Error calculation for programmed baud rates at f
Baud rate
S.No Desired
1. 2.4 KBps 2.400 KBps
2. 9.6 KBps 9.604 KBps
3. 19.2 KBps 19.185 KBps
4. 57.6 KBps 57.554 KBps
5. 115.2 KBps 115.942 KBps 4.3125
228.571
6. 230.4 KBps
KBps
470.588
7. 460.8 KBps
KBps
8. 896 KBps NA
9. 921.6 KBps NA
10. 1.792 MBps NA
11. 1.8432 MBps NA
12. 3.584 MBps NA
13. 3.6864 MBps NA
14. 7.168 MBps NA
15. 7.3728 MBps NA
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.
Table 139. 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
Universal synchronous asynchronous receiver transmitter (USART)

oversampling by 16

Oversampling by 16 (OVER8=0)
f = 8 MHz
PCLK
Value
programme
Actual d in the
baud rate
register
208.3125
52.0625
26.0625
8.6875
2.1875
1.0625
NA
NA
NA
NA
NA
NA
NA
NA

oversampling by 8

Oversampling by 8 (OVER8=1)
f = 8 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
2.400 KBps 416.625
9.604 KBps 104.125
19.185 KBps 52.125
(1)
% Error =
(Calculated -
Desired)B.Rate
/Desired B.Rate
0.00%
0.04%
0.08%
0.08%
0.64%
0.79%
2.12%
NA
NA
NA
NA
NA
NA
NA
NA
(1)
% Error =
(Calculated -
Desired)B.Rate
/Desired B.Rate
0.01%
0.04%
0.08%
RM0090 Rev 18
= 8 MHz or f
PCLK PCLK
f = 16 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
2.400 KBps 416.6875
9.598 KBps 104.1875
19.208 KBps 52.0625
57.554 KBps 17.3750
115.108 KBps 8.6875
231.884 KBps 4.3125
457.143 KBps 2.1875
888.889 KBps 1.1250
941.176 KBps 1.0625
NA NA
NA NA
NA NA
NA NA
NA NA
NA NA
= 8 MHz or f
PCLK PCLK
f = 16 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
2.400 KBps 833.375
9.598 KBps 208.375
19.208 KBps 104.125
= 16 MHz,
% Error
0.00%
0.02%
0.04%
0.08%
0.08%
0.64%
0.79%
0.79%
2.12%
NA
NA
NA
NA
NA
NA
= 16 MHz,
%
Error
0.00%
0.02%
0.04%
983/1749
1018