Oversampling By 16 - ST STM32F413 Reference Manual

RM0430
Table 145. Error calculation for programmed baud rates at f
Baud rate7
S.No Desired
1 1.2 KBps
2 2.4 KBps
3 9.6 KBps
4 19.2 KBps 19.185 KBps
5 38.4 KBps 38.462 KBps
6 57.6 KBps 57.554 KBps
7 115.2 KBps 115.942 KBps
8 230.4 KBps 228.571 KBps
9 460.8 KBps 470.588 KBps
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 146. 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
8 230.4 KBps
Universal synchronous asynchronous receiver transmitter (USART)

oversampling by 16

Oversampling by 16 (OVER8=0)
f = 8 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
1.2 KBps 416.6875
2.4 KBps 208.3125
9.604 KBps 52.0625
26.0625
13
8.6875
4.3125
2.1875
1.0625
oversampling by 8
Oversampling by 8 (OVER8 = 1)
f = 8 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
1.2 KBps 833.375
2.4 KBps 416.625
9.604 KBps 104.125
19.185 KBps 52.125
38.462 KBps
57.554 KBps 17.375
115.942 KBps 8.625
228.571 KBps 4.375
DocID029473 Rev 3
(1)
% Error =
(Calculated -
Desired) B.rate /
Desired B.rate
0
0.01
0.04
0.08
0.16
0.08
0.64
0.79
2.12
(1)
% Error =
(Calculated -
Desired)
B.rate /
Desired
B.rate
0
0.01
0.04
0.08
26 0.16
0.08
0.64
0.79
= 8 MHz or f
PCLK PCLK
f = 12 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
1.2 KBps 625
2.4 KBps 312.5
9.6 KBps 78.125
19.2 KBps 39.0625
38.339 KBps 19.5625
57.692 KBps 13
115.385 KBps 6.5
230.769 KBps 3.25
461.538 KBps 1.625
= 8 MHz or f
PCLK PCLK
f = 12 MHz
PCLK
Value
programmed
Actual
in the baud
rate register
1.2 KBps 1250
2.4 KBps 625
9.6 KBps 156.25
19.2 KBps 78.125
38.339 KBps 39.125
57.692 KBps 26
115.385 KBps 13
230.769 KBps 6.5
= 12 MHz,
% Error
0
0
0
0
0.16
0.16
0.16
0.16
0.16
= 12 MHz,
% Error
0
0
0
0
0.16
0.16
0.16
0.16
871/1284
906