ATmega64A
20.10 Examples of Baud Rate Setting
For standard crystal and resonator frequencies, the most commonly used baud rates for asyn-
chronous operation can be generated by using the UBRRn settings in Table 20-4 on page 192 to
Table 20-7 on page 195. UBRRn values which yield an actual baud rate differing less than 0.5%
from the target baud rate, are bold in the table. Higher error ratings are acceptable, but the
receiver will have less noise resistance when the error ratings are high, especially for large serial
frames (see “Asynchronous Operational Range” on page 189). The error values are calculated
using the following equation:
BaudRateClosest Match
⎛
⎞
Error[%] = ------------------------------------------------------- – 1 • 100%
⎝
⎠
BaudRate
Table 20-4. Examples of UBRR Settings for Commonly Used Oscillator Frequencies
fosc = 1.0000 MHz fosc = 1.8432 MHz
U2X = 0 U2X = 1 U2X = 0 U2X = 1
UBRRn Errorn UBRRn Error UBRRn Error UBRRn
fosc = 2.0000 MHz
U2X = 0 U2X = 1
UBRRn Error
Baud
Rate
(bps)
UBRRn
Error
0.2%
0.2%
-7.0%
8.5%
8.5%
8.5%
-18.6%
8.5%
–
Error
0.2%
0.2%
0.2%
-3.5%
-7.0%
8.5%
8.5%
8.5%
-18.6%
8.5%
–
2400
25
12
6
51
25
12
8
0.2%
0.2%
0.2%
-3.5%
-7.0%
8.5%
8.5%
8.5%
-18.6%
8.5%
–
47
23
11
7
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
-25.0%
0.0%
–
95
47
23
15
11
7
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
–
51
25
12
8
103
51
25
16
12
8
0.2%
0.2%
0.2%
2.1%
0.2%
-3.5%
-7.0%
8.5%
8.5%
8.5%
–
4800
9600
14.4k
19.2k
28.8k
38.4k
57.6k
76.8k
115.2k
230.4k
250k
3
2
6
5
6
1
3
3
3
1
2
2
5
2
6
0
1
1
3
1
3
–
1
1
2
1
2
–
–
0
0
1
0
1
–
–
–
–
0
–
–
–
–
–
–
–
–
–
–
–
0
0.0%
Max (1)
62.5 kbps
UBRR = 0, Error = 0.0%
125 kbps
115.2 kbps
230.4 kbps
125 kbps
250 kbps
1.
192
8160C–AVR–07/09
ATMEL [ ATMEL ]
