
186
2552K–AVR–04/11
ATmega329/3290/649/6490
Do not use Read-Modify-Write instructions (SBI and CBI) to set or clear the MPCMn bit. The
MPCMn bit shares the same I/O location as the TXCn Flag and this might accidentally be
cleared when using SBI or CBI instructions.
19.10 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 19-4. 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 resis-
tance when the error ratings are high, especially for large serial frames (see
“AsynchronousError[%]
BaudRate
Closest Match
BaudRate
--------------------------------------------------------
1
–
100%
=
Table 19-4.
Examples of UBRRn Settings for Commonly Used Oscillator Frequencies
Baud
Rate
(bps)
f
osc = 1.0000MHz
f
osc = 1.8432MHz
f
osc = 2.0000MHz
U2Xn = 0
U2Xn = 1
U2Xn = 0
U2Xn = 1
U2Xn = 0
U2Xn = 1
UBRRn
Error
UBRRn
Error
UBRRn
Error
UBRRn
Error
UBRRn
Error
UBRRn
Error
2400
25
0.2%
51
0.2%
47
0.0%
95
0.0%
51
0.2%
103
0.2%
4800
12
0.2%
25
0.2%
23
0.0%
47
0.0%
25
0.2%
51
0.2%
9600
6
-7.0%
12
0.2%
11
0.0%
23
0.0%
12
0.2%
25
0.2%
14.4k
3
8.5%
8
-3.5%
70.0%
15
0.0%
8
-3.5%
16
2.1%
19.2k
2
8.5%
6
-7.0%
50.0%
11
0.0%
6
-7.0%
12
0.2%
28.8k1
8.5%
3
8.5%
3
0.0%
7
0.0%
3
8.5%
8
-3.5%
38.4k
1
-18.6%
2
8.5%
2
0.0%
5
0.0%
2
8.5%
6
-7.0%
57.6k
0
8.5%
1
8.5%
1
0.0%
3
0.0%
1
8.5%
3
8.5%
76.8k
––1
-18.6%
1
-25.0%
20.0%
1-18.6%
2
8.5%
115.2k
–
0
8.5%
0
0.0%
1
0.0%
0
8.5%
1
8.5%
230.4k
–––
00.0%
––
–
250k
–––
–
0
0.0%
Max. (1)
62.5kbps
125kbps
115.2kbps
230.4kbps
125kbps
250kbps
1.
UBRR = 0, Error = 0.0%