Examples Of Ubrr Settings For Commonly Used Oscillator Frequencies - Atmel ATmega128 Manual

Table 83. Examples of UBRR Settings for Commonly Used Oscillator Frequencies
f = 3.6864 MHz
osc
Baud
U2X = 0
Rate
(bps) UBRR Error
2400 95 0.0%
4800 47 0.0%
9600 23 0.0%
14.4k 15 0.0%
19.2k 11 0.0%
28.8k 7 0.0%
38.4k 5 0.0%
57.6k 3 0.0%
76.8k 2 0.0%
115.2k 1 0.0%
230.4k 0 0.0%
250k 0 -7.8%
0.5M – –
1M – –
(1)
Max 230.4 kbps
1. UBRR = 0, Error = 0.0%
2467S–AVR–07/09
U2X = 1 U2X = 0
UBRR Error UBRR
191 0.0% 103
95 0.0% 51
47 0.0% 25
31 0.0% 16
23 0.0% 12
15 0.0% 8
11 0.0% 6
7 0.0% 3
5 0.0% 2
3 0.0% 1
1 0.0% 0
1 -7.8% 0
0 -7.8% –
– – –
460.8 kbps 250 kbps
f = 4.0000 MHz
osc
U2X = 1
Error UBRR Error
0.2% 207 0.2%
0.2% 103 0.2%
0.2% 51 0.2%
2.1% 34 -0.8%
0.2% 25 0.2%
-3.5% 16 2.1%
-7.0% 12 0.2%
8.5% 8 -3.5%
8.5% 6 -7.0%
8.5% 3 8.5%
8.5% 1 8.5%
0.0% 1 0.0%
– 0 0.0%
– – –
0.5 Mbps
ATmega128
f = 7.3728 MHz
osc
U2X = 0 U2X = 1
UBRR Error UBRR
191 0.0% 383
95 0.0% 191
47 0.0% 95
31 0.0% 63
23 0.0% 47
15 0.0% 31
11 0.0% 23
7 0.0% 15
5 0.0% 11
3 0.0% 7
1 0.0% 3
1 -7.8% 3
0 -7.8% 1
– – 0
460.8 kbps 921.6 kbps
Error
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
-7.8%
-7.8%
-7.8%
195