Atmel AT90S2313 - Baud Rate Generator Functionality

AT90S2313
44
Baud Rate Generator
The baud rate generator is a frequency divider which generates baud-rates according to the following equation:
• BAUD = Baud-Rate
•f
CK
= Crystal Clock frequency
• UBRR = Contents of the UART Baud Rate register, UBRR (0-255)
For standard crystal frequencies, the most commonly used baud rates can be generated by using the UBRR settings in
Table 15. UBRR values which yield an actual baud rate differing less than 2% from the target baud rate, are bold in the
table. However, using baud rates that have more than 1% error is not recommended. High error ratings give less noise
resistance.
Table 15. UBRR Settings at Various Crystal Frequencies
BAUD
f
CK
16(UBRR 1)+
-------------------------------------=
Baud Rate
1MHz
%Error
1.8432 MHz
%Error
2MHz
%Error
2.4576 MHz
%Error
2400
UBRR=
25 0.2
UBRR=
47 0.0
UBRR=
51 0.2
UBRR=
63 0.0
4800
UBRR=
12 0.2
UBRR=
23 0.0
UBRR=
25 0.2
UBRR=
31 0.0
9600
UBRR= 6 7.5 UBRR=
11 0.0
UBRR=
12 0.2
UBRR=
15 0.0
14400
UBRR= 3 7.8 UBRR=
70.0
UBRR= 8 3.7 UBRR= 10 3.1
19200
UBRR= 2 7.8 UBRR=
50.0
UBRR= 6 7.5 UBRR=
70.0
28800
UBRR= 1 7.8 UBRR=
30.0
UBRR= 3 7.8 UBRR= 4 6.3
38400
UBRR= 1 22.9 UBRR=
20.0
UBRR= 2 7.8 UBRR=
30.0
57600
UBRR= 0 7.8 UBRR=
10.0
UBRR= 1 7.8 UBRR= 2 12.5
76800
UBRR= 0 22.9 UBRR= 1 33.3 UBRR= 1 22.9 UBRR=
10.0
115200
UBRR= 0 84.3 UBRR=
00.0
UBRR= 0 7.8 UBRR= 0 25.0
Baud Rate
3.2768 MHz
%Error
3.6864 MHz
%Error
4MHz
%Error
4.608 MHz
%Error
2400
UBRR=
84 0.4
UBRR=
95 0.0
UBRR=
103 0.2
UBRR=
119 0.0
4800
UBRR=
42 0.8
UBRR=
47 0.0
UBRR=
51 0.2
UBRR=
59 0.0
9600
UBRR=
20 1.6
UBRR=
23 0.0
UBRR=
25 0.2
UBRR=
29 0.0
14400
UBRR=
13 1.6
UBRR=
15 0.0
UBRR= 16 2.1 UBRR=
19 0.0
19200
UBRR= 10 3.1 UBRR=
11 0.0
UBRR=
12 0.2
UBRR=
14 0.0
28800
UBRR=
61.6
UBRR=
70.0
UBRR= 8 3.7 UBRR=
90.0
38400
UBRR= 4 6.3 UBRR=
50.0
UBRR= 6 7.5 UBRR= 7 6.7
57600
UBRR= 3 12.5 UBRR=
30.0
UBRR= 3 7.8 UBRR=
40.0
76800
UBRR= 2 12.5 UBRR=
20.0
UBRR= 2 7.8 UBRR= 3 6.7
115200
UBRR= 1 12.5 UBRR=
10.0
UBRR= 1 7.8 UBRR= 2 20.0
Baud Rate
7.3728 MHz
%Error
8MHz
%Error
9.216 MHz
%Error
11.059 MHz
%Error
2400
UBRR=
191 0.0
UBRR=
207 0.2
UBRR=
239 0.0
UBRR= 287 -
4800
UBRR=
95 0.0
UBRR=
103 0.2
UBRR=
119 0.0
UBRR=
143 0.0
9600
UBRR=
47 0.0
UBRR=
51 0.2
UBRR=
59 0.0
UBRR=
71 0.0
14400
UBRR=
31 0.0
UBRR=
34 0.8
UBRR=
39 0.0
UBRR=
47 0.0
19200
UBRR=
23 0.0
UBRR=
25 0.2
UBRR=
29 0.0
UBRR=
35 0.0
28800
UBRR=
15 0.0
UBRR= 16 2.1 UBRR=
19 0.0
UBRR=
23 0.0
38400
UBRR=
11 0.0
UBRR=
12 0.2
UBRR=
14 0.0
UBRR=
17 0.0
57600
UBRR=
70.0
UBRR= 8 3.7 UBRR=
90.0
UBRR=
11 0.0
76800
UBRR=
50.0
UBRR= 6 7.5 UBRR= 7 6.7 UBRR=
80.0
115200
UBRR=
30.0
UBRR= 3 7.8 UBRR=
40.0
UBRR=
50.0