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Table 15. UBRR Settings at Various Crystal Frequencies
Baud Rate
2400 UBRR=
4800 UBRR=
9600 UBRR=
14400 UBRR=
19200 UBRR=
28800 UBRR=
38400 UBRR=
57600 UBRR=
76800 UBRR=
115200 UBRR=
Baud Rate 3.2768 MHz %Error
2400 UBRR=
4800 UBRR=
9600 UBRR=
14400 UBRR=
19200 UBRR=
28800 UBRR=
38400 UBRR=
57600 UBRR=
76800 UBRR=
115200 UBRR=
Baud Rate 7.3728 MHz %Error
2400 UBRR=
4800 UBRR=
9600 UBRR=
14400 UBRR=
19200 UBRR=
28800 UBRR=
38400 UBRR=
57600 UBRR=
76800 UBRR=
115200 UBRR=
UART Baud Rate Register –
UBRR
0839G–08/01
1 MHz %Error
1.8432 MHz %Error
25
0.2 UBRR=
0.2 UBRR=
12
6
7.5 UBRR=
3
7.8 UBRR=
2
7.8 UBRR=
1
7.8 UBRR=
1
22.9 UBRR=
0
7.8 UBRR=
0
22.9 UBRR=
0
84.3 UBRR=
3.6864 MHz %Error
0.4 UBRR=
84
42
0.8 UBRR=
20
1.6 UBRR=
13
1.6 UBRR=
10
3.1 UBRR=
1.6 UBRR=
6
4
6.3 UBRR=
3
12.5 UBRR=
2
12.5 UBRR=
1
12.5 UBRR=
8 MHz %Error
0.0 UBRR=
191
95
0.0 UBRR=
0.0 UBRR=
47
31
0.0 UBRR=
0.0 UBRR=
23
15
0.0 UBRR=
0.0 UBRR=
11
7
0.0 UBRR=
0.0 UBRR=
5
3
0.0 UBRR=
Bit
7
$09 ($29)
MSB
Read/Write
R/W
Initial value
0
The UBRR register is an 8-bit read/write register that specifies the UART Baud Rate
according to the formula on the previous page.
2 MHz %Error
47
0.0 UBRR=
0.0 UBRR=
23
11
0.0 UBRR=
0.0 UBRR=
7
5
0.0 UBRR=
0.0 UBRR=
3
2
0.0 UBRR=
0.0 UBRR=
1
1
33.3 UBRR=
0.0 UBRR=
0
4 MHz %Error
0.0 UBRR=
95
103
47
0.0 UBRR=
23
0.0 UBRR=
15
0.0 UBRR=
11
0.0 UBRR=
0.0 UBRR=
7
5
0.0 UBRR=
0.0 UBRR=
3
2
0.0 UBRR=
0.0 UBRR=
1
9.216 MHz %Error
0.2 UBRR=
207
239
103
0.2 UBRR=
119
0.2 UBRR=
51
34
0.8 UBRR=
0.2 UBRR=
25
16
2.1 UBRR=
0.2 UBRR=
12
8
3.7 UBRR=
6
7.5 UBRR=
3
7.8 UBRR=
6
5
4
R/W
R/W
R/W
0
0
0
AT90S2313
2.4576 MHz %Error
51
0.2 UBRR=
63
0.2 UBRR=
25
31
12
0.2 UBRR=
15
8
3.7 UBRR=
10
6
7.5 UBRR=
3
7.8 UBRR=
2
7.8 UBRR=
1
7.8 UBRR=
1
22.9 UBRR=
0
7.8 UBRR=
4.608 MHz %Error
0.2 UBRR=
119
51
0.2 UBRR=
59
25
0.2 UBRR=
29
16
2.1 UBRR=
19
12
0.2 UBRR=
14
8
3.7 UBRR=
6
7.5 UBRR=
3
7.8 UBRR=
2
7.8 UBRR=
1
7.8 UBRR=
11.059 MHz %Error
0.0 UBRR=
287
0.0 UBRR=
143
0.0 UBRR=
59
71
39
0.0 UBRR=
47
0.0 UBRR=
29
35
19
0.0 UBRR=
23
0.0 UBRR=
14
17
9
0.0 UBRR=
11
7
6.7 UBRR=
4
0.0 UBRR=
3
2
1
R/W
R/W
R/W
0
0
0
0.0
0.0
0.0
3.1
7
0.0
4
6.3
3
0.0
2
12.5
1
0.0
0
25.0
0.0
0.0
0.0
0.0
0.0
9
0.0
7
6.7
4
0.0
3
6.7
2
20.0
-
0.0
0.0
0.0
0.0
0.0
0.0
0.0
8
0.0
5
0.0
0
LSB
UBRR
R/W
0
49
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