Universal synchronous asynchronous receiver transmitter (USART)
RM0090
974/1731
DocID018909 Rev 11
Table 134. Error calculation for programmed baud rates at f
PCLK
= 8 MHz or f
PCLK
=12 MHz,
oversampling by 8
(1)
Oversampling by 8 (OVER8 = 1)
Baud rate
f
PCLK
= 8 MHz
f
PCLK
= 12 MHz
S.No
Desired
Actual
Value
programmed
in the baud
rate register
% Error =
(Calculated -
Desired)
B.rate /
Desired
B.rate
Actual
Value
programmed
in the baud
rate register
% Error
1
1.2 KBps
1.2 KBps
833.375
0
1.2 KBps
1250
0
2
2.4 KBps
2.4 KBps
416.625
0.01
2.4 KBps
625
0
3
9.6 KBps
9.604 KBps
104.125
0.04
9.6 KBps
156.25
0
4
19.2 KBps
19.185 KBps
52.125
0.08
19.2 KBps
78.125
0
5
38.4 KBps
38.462 KBps
26
0.16
38.339 KBps
39.125
0.16
6
57.6 KBps
57.554 KBps
17.375
0.08
57.692 KBps
26
0.16
7
115.2 KBps
115.942 KBps
8.625
0.64
115.385 KBps
13
0.16
8
230.4 KBps
228.571 KBps
4.375
0.79
230.769 KBps
6.5
0.16
9
460.8 KBps
470.588 KBps
2.125
2.12
461.538 KBps
3.25
0.16
10
921.6 KBps
888.889 KBps
1.125
3.55
923.077 KBps
1.625
0.16
11
2 MBps
NA
NA
NA
NA
NA
NA
12
3 MBps
NA
NA
NA
NA
NA
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 135. Error calculation for programmed baud rates at f
PCLK
= 16 MHz or f
PCLK
= 24 MHz,
oversampling by 16
(1)
Oversampling by 16 (OVER8 = 0)
Baud rate
fPCLK
= 16 MHz
fPCLK
= 24 MHz
S.No
Desired
Actual
Value
programmed
in the baud
rate register
% Error =
(Calculated -
Desired) B.rate /
Desired B.rate
Actual
Value
programmed
in the baud
rate register
% Error
1
1.2 KBps
1.2 KBps
833.3125
0
1.2
1250
0
2
2.4 KBps
2.4 KBps
416.6875
0
2.4
625
0
3
9.6 KBps
9.598 KBps
104.1875
0.02
9.6
156.25
0
4
19.2 KBps
19.208 KBps
52.0625
0.04
19.2
78.125
0
5
38.4 KBps
38.369 KBps
26.0625
0.08
38.4
39.0625
0
6
57.6 KBps
57.554 KBps
17.375
0.08
57.554
26.0625
0.08