ATmega169P
18.10 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 18-9. UBRRn
values which yield an actual baud rate differing less than 0.5ꢀ from the target baud rate, are
bold in the table. Higher error ratings are acceptable, but the Receiver will have less noise resis-
tance when the error ratings are high, especially for large serial frames (see ”Asynchronous
Operational Range” on page 186). The error values are calculated using the following equation:
BaudRateClosest Match
⎛
⎞
Error[ꢀ] = ------------------------------------------------------- – 1 • 100ꢀ
⎝
⎠
BaudRate
Table 18-9. Examples of UBRRn Settings for Commonly Used Oscillator Frequencies
fosc = 1.0000 MHz fosc = 1.8432 MHz
U2Xn = 0 U2Xn = 1
UBRRn Error UBRRn Error UBRRn Error
fosc = 2.0000 MHz
Baud
Rate
(bps)
U2Xn = 0
UBRRn Error
U2Xn = 1
U2Xn = 0
U2Xn = 1
UBRRn Error
UBRRn Error
2400
25
12
6
0.2ꢀ
0.2ꢀ
-7.0ꢀ
8.5ꢀ
8.5ꢀ
8.5ꢀ
-18.6ꢀ
8.5ꢀ
–
51
25
12
8
0.2ꢀ
0.2ꢀ
0.2ꢀ
-3.5ꢀ
-7.0ꢀ
8.5ꢀ
8.5ꢀ
8.5ꢀ
-18.6ꢀ
8.5ꢀ
–
47
23
11
7
0.0ꢀ
0.0ꢀ
0.0ꢀ
0.0ꢀ
0.0ꢀ
0.0ꢀ
0.0ꢀ
0.0ꢀ
-25.0ꢀ
0.0ꢀ
–
95
47
23
15
11
7
0.0ꢀ
0.0ꢀ
0.0ꢀ
0.0ꢀ
0.0ꢀ
0.0ꢀ
0.0ꢀ
0.0ꢀ
0.0ꢀ
0.0ꢀ
0.0ꢀ
–
51
25
12
8
0.2ꢀ
0.2ꢀ
0.2ꢀ
-3.5ꢀ
-7.0ꢀ
8.5ꢀ
8.5ꢀ
8.5ꢀ
-18.6ꢀ
8.5ꢀ
–
103
51
25
16
12
8
0.2ꢀ
0.2ꢀ
0.2ꢀ
2.1ꢀ
0.2ꢀ
-3.5ꢀ
-7.0ꢀ
8.5ꢀ
8.5ꢀ
8.5ꢀ
–
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
0.0ꢀ
Max.(1)
62.5 kbps
1. UBRRn = 0, Error = 0ꢀ.
125 kbps
115.2 kbps
230.4 kbps
125 kbps
250 kbps
Note:
195
8018A–AVR–03/06
ATMEL [ ATMEL ]
