ST STM32F207 Series Reference Manual page 648

Universal synchronous asynchronous receiver transmitter (USART)
Table 89. 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 90. 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
648/1381
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
PCLK
(1)
% Error =
(Calculated -
Desired)B.Rate
/Desired B.Rate
0.00% 2.400 KBps
0.04% 9.598 KBps
0.08% 19.208 KBps
0.08% 57.554 KBps
0.64% 115.108 KBps
0.79% 231.884 KBps
2.12% 457.143 KBps
NA 888.889 KBps
NA 941.176 KBps
NA NA
NA NA
NA NA
NA NA
NA NA
NA NA
PCLK
(1)
% Error =
(Calculated -
Desired)B.Rate
/Desired B.Rate
0.01%
0.04%
0.08%
RM0033 Rev 9
= 8 MHz or f
PCLK
f = 16 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
416.6875
104.1875
52.0625
17.3750
8.6875
4.3125
2.1875
1.1250
1.0625
NA
NA
NA
NA
NA
NA
= 8 MHz or f
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
RM0033
= 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%