Oversampling By 16 - STMicroelectronics STM32F405 Reference Manual

RM0090
Table 138. Error calculation for programmed baud rates at f
Baud rate
S.No Desired
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
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.
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
4. 57.6 KBps
5. 115.2 KBps
6. 230.4 KBps
7. 460.8 KBps
Universal synchronous asynchronous receiver transmitter (USART)
oversampling by 8
Oversampling by 8 (OVER8=1)
f
PCLK
Value
programmed
Actual
in the baud
rate register
57.557 KBps 17.375
115.942 KBps 8.625
228.571 KBps 4.375
470.588 KBps 2.125
888.889 KBps 1.125
888.889 KBps 1.125
NA NA
NA NA
NA NA
NA NA
NA NA
NA NA

oversampling by 16

Oversampling by 16 (OVER8=0)
f = 30 MHz
PCLK
Value
programme
Actual d in the
baud rate
register
2.400 KBps 781.2500
9.600 KBps 195.3125
19.194 KBps 97.6875
57.582KBps 32.5625
115.385 KBps 16.2500
230.769 KBps 8.1250
461.538 KBps 4.0625
DocID018909 Rev 11
(1)
(continued)
= 8 MHz
% Error =
(Calculated -
Desired)B.Rate
/Desired B.Rate
0.08%
0.64%
0.79%
2.12%
0.79%
3.55%
NA
NA
NA
NA
NA
NA
(1)(2)
% Error =
(Calculated -
Desired)B.Rate
/Desired B.Rate
0.00%
0.00%
0.03%
0.03%
0.16%
0.16%
0.16%
= 8 MHz or f
PCLK PCLK
f = 16 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
57.554 KBps 34.750
115.108 KBps 17.375
231.884 KBps 8.625
457.143 KBps 4.375
888.889 KBps 2.250
941.176 KBps 2.125
1.7777 MBps 1.125
1.7777 MBps 1.125
NA NA
NA NA
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 1562.5000
9.600 KBps 390.6250
19.200 KBps 195.3125
57.582 KBps 65.1250
115.163 KBps 32.5625
230.769KBps 16.2500
461.538 KBps 8.1250
= 16 MHz,
%
Error
0.08%
0.08%
0.64%
0.79%
0.79%
2.12%
0.79%
3.55%
NA
NA
NA
NA
= 60 MHz,
%
Error
0.00%
0.00%
0.00%
0.03%
0.03%
0.16%
0.16%
977/1731
1010