Oversampling By 8 - STMicroelectronics STM32F405 Reference Manual

RM0090
Table 135. Error calculation for programmed baud rates at f
Baud rate
S.No Desired
7 115.2 KBps
8 230.4 KBps
9 460.8 KBps
10 921.6 KBps
11 2 MBps
12 3 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 136. Error calculation for programmed baud rates at f
Baud rate
S.No Desired
1 1.2 KBps
2 2.4 KBps
3 9.6 KBps
4 19.2 KBps
5 38.4 KBps
6 57.6 KBps
7 115.2 KBps 115.108 KBps
8 230.4 KBps 231.884 KBps
9 460.8 KBps 457.143 KBps
10 921.6 KBps 941.176 KBps
11 2 MBps
12 3 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.
Universal synchronous asynchronous receiver transmitter (USART)
oversampling by 16
Oversampling by 16 (OVER8 = 0)
f PCLK
Value
programmed
Actual
in the baud
rate register
115.108 KBps 8.6875
231.884 KBps 4.3125
457.143 KBps 2.1875
941.176 KBps 1.0625
NA
NA

oversampling by 8

Oversampling by 8 (OVER8=1)
f = 16 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
1.2 KBps 1666.625
2.4 KBps 833.375
9.598 KBps 208.375
19.208 KBps 104.125
38.369 KBps 52.125
57.554 KBps 34.75
17.375
8.625
4.375
2.125
2000 KBps 1
NA NA
DocID018909 Rev 11
(1)
(continued)
= 16 MHz
% Error =
(Calculated -
Desired) B.rate /
Desired B.rate
0.08
0.64
0.79
2.12
NA NA
NA NA
(1)
% Error =
(Calculated -
Desired) B.rate /
Desired B.rate
0
0
0.02
0.04
0.08
0.08
0.08
0.64
0.79
2.12
0
NA
= 16 MHz or f
PCLK PCLK
= 24 MHz
f PCLK
Value
programmed
Actual
in the baud
rate register
115.385 13
230.769 6.5
461.538 3.25
923.077 1.625
NA NA
NA NA
= 16 MHz or f
PCLK PCLK
f = 24 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
1.2 KBps 2500
2.4 KBps 1250
9.6 KBps 312.5
19.2 KBps 156.25
38.4 KBps 78.125
57.554 KBps 52.125
115.385 KBps 26
230.769 KBps 13
461.538 KBps 6.5
923.077 KBps 3.25
2000 KBps 1.5
3000 KBps
= 24 MHz,
% Error
0.16
0.16
0.16
0.16
NA
NA
= 24 MHz,
% Error
0
0
0
0
0
0.08
0.16
0.16
0.16
0.16
0
1 0
975/1731
1010