ATmega163(L)
65
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
• UBR = Contents of the UBRRHI and UBRR registers, (0-4095)
• Note that this equation is not valid when the UART transmission speed is doubled. See “Double Speed Transmission” on
page 66 for a detailed description.
For standard crystal frequencies, the most commonly used baud rates can be generated by using the UBR settings in
Table 27. UBR 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 27. UBR Settings at Various Crystal Frequencies
BAUD
f
CK
16(UBR 1 )+
---------------------------------
=
Baud Rate
1MHz
%Error
1,84 MHz
%Error
2MHz
%Error
2,458 MHz
%Error
2400
UBR=
25 0,2
UBR=
47 0,0
UBR=
51 0,2
UBR=
63 0,0
4800
UBR=
12 0,2
UBR=
23 0,0
UBR=
25 0,2
UBR=
31 0,0
9600
UBR= 6 7,5 UBR=
11 0,0
UBR=
12 0,2
UBR=
15 0,0
14400
UBR= 3 7,8 UBR=
70,0
UBR= 8 3,7 UBR= 10 3,1
19200
UBR= 2 7,8 UBR=
50,0
UBR= 6 7,5 UBR=
70,0
28800
UBR= 1 7,8 UBR=
30,0
UBR= 3 7,8 UBR= 4 6,3
38400
UBR= 1 22,9 UBR=
20,0
UBR= 2 7,8 UBR=
30,0
57600
UBR= 0 7,8 UBR=
10,0
UBR= 1 7,8 UBR= 2 12,5
76800
UBR= 0 22,9 UBR= 1 33,3 UBR= 1 22,9 UBR=
10,0
115200
UBR= 0 84,3 UBR=
00,0
UBR= 0 7,8 UBR= 0 25,0
Baud Rate
3,28 MHz
%Error
3,69 MHz
%Error
4MHz
%Error
4,608 MHz
%Error
2400
UBR=
84 0,4
UBR=
95 0,0
UBR=
103 0,2
UBR=
119 0,0
4800
UBR=
42 0,8
UBR=
47 0,0
UBR=
51 0,2
UBR=
59 0,0
9600
UBR=
20 1,6
UBR=
23 0,0
UBR=
25 0,2
UBR=
29 0,0
14400
UBR=
13 1,6
UBR=
15 0,0
UBR= 16 2,1 UBR=
19 0,0
19200
UBR= 10 3,1 UBR=
11 0,0
UBR=
12 0,2
UBR=
14 0,0
28800
UBR=
61,6
UBR=
70,0
UBR= 8 3,7 UBR=
90,0
38400
UBR= 4 6,3 UBR=
50,0
UBR= 6 7,5 UBR= 7 6,7
57600
UBR= 3 12,5 UBR=
30,0
UBR= 3 7,8 UBR=
40,0
76800
UBR= 2 12,5 UBR=
20,0
UBR= 2 7,8 UBR= 3 6,7
115200
UBR= 1 12,5 UBR=
10,0
UBR= 1 7,8 UBR= 2 20,0
Baud Rate
7,37 MHz
%Error
8MHz
%Error
2400
UBR=
191 0,0
UBR=
207 0,2
4800
UBR=
95 0,0
UBR=
103 0,2
9600
UBR=
47 0,0
UBR=
51 0,2
14400
UBR=
31 0,0
UBR=
34 0,8
19200
UBR=
23 0,0
UBR=
25 0,2
28800
UBR=
15 0,0
UBR= 16 2,1
38400
UBR=
11 0,0
UBR=
12 0,2
57600
UBR=
70,0
UBR= 8 3,7
76800
UBR=
50,0
UBR= 6 7,5
115200
UBR=
30,0
UBR= 3 7,8
(30 Seiten)
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