Table 85. Error Calculation For Programmed Baud Rates At F - STMicroelectronics STM32F05 series Reference Manual

Universal synchronous asynchronous receiver transmitter (USART)
Example 2
To obtain 921.6 Kbaud with f
●
In case of oversampling by 16:
USARTDIV = 48 000 000/921 600
BRR = USARTDIV = 52d = 0x34
●
In case of oversampling by 8:
USARTDIV = 2 * 48 000 000/921 600
USARTDIV = 104 (104d = 0x68)
BRR[3:0] = USARTDIV[3:0] >> 1 = 0x8 >>1 = 0x4
BRR = 0x64
Table 85. Error calculation for programmed baud rates at f
for oversampling by 16 and by 8
Baudrate
S.No Desired Actual
2 2.4
3 9.6
4 19.2
5 38.4
6 57.6 57.62
7 115.2 115.11
8 230.4 230.76
9 460.8 461.54
10 921.6 923.07
11 2000
12 3000
13 4000
14 5000
15 6000
586/742
CK
Oversampling by 16 (OVER8 = 0)
USART_
BRR value
baudrate)/Desired
2.4 0x4E20
9.6 0x1388
19.2 0x9C4
38.4 0x4E2
0x341
0x1A1
0xD0
0x68
0x34
2000 0x18
3000 0x10
N.A N.A
N.A N.A
N.A N.A
Doc ID 018940 Rev 1
= 48 MHz.
CK
% Error =
(calculated -
Desired Actual
baudrate
0 2.4
0 9.6
0 19.2
0 38.4
0.03 57.59
0.08 115.25
0.16 230.21
0.16 461.54
0.16 923.07
0 2000
0 3000
N.A 4000
N.A 5052.63
N.A 6000
= 48 MHz
Oversampling by 8 (OVER8 = 1)
(calculated -
USART_
BRR value
baudrate)/Desired
0x9C40
0x2710
0x1384
0x9C2
0x681
0x340
0x1A0
0xD0
0x64
0x30
0x20
0x14
0x11
0x10
RM0091
% Error =
Desired
baudrate
0
0
0
0
0.02
0.04
0.08
0.16
0.16
0
0
0
1.05
0