AT90CAN128
Examples of Baud Rate
Setting
For standard crystal, resonator and external oscillator frequencies, the most commonly
used baud rates for asynchronous operation can be generated by using the UBRRn set-
tings in Table 84 up to Table 87. 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
186). The error values are calculated using the following equation:
BaudRateClosest Match
⎛
⎞
Error[%] = 1 – ------------------------------------------------------- • 100%
⎝
⎠
BaudRate
Table 84. Examples of UBRRn Settings for Commonly Frequencies
fclkio = 1.0000 MHz
fclkio = 1.8432 MHz
fclkio = 2.0000 MHz
Baud
Rate
U2Xn = 0
U2Xn = 1
U2Xn = 0
UBRRn Error
U2Xn = 1
U2Xn = 0
UBRRn Error
U2Xn = 1
(bps) UBRRn Error
UBRRn Error
UBRRn Error
UBRRn Error
2400
4800
25
12
6
0.2%
0.2%
-7.0%
8.5%
8.5%
8.5%
-18.6%
8.5%
–
51
25
12
8
0.2%
47
23
11
7
0.0%
95
47
23
15
11
7
0.0%
51
25
12
8
0.2%
103
51
25
16
12
8
0.2%
0.2%
0.2%
-3.5%
-7.0%
8.5%
8.5%
8.5%
-18.6%
8.5%
–
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
-25.0%
0.0%
–
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
–
0.2%
0.2%
-3.5%
-7.0%
8.5%
8.5%
8.5%
-18.6%
8.5%
–
0.2%
0.2%
2.1%
0.2%
-3.5%
-7.0%
8.5%
8.5%
8.5%
–
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
–
–
–
–
–
–
–
–
–
–
–
–
–
500k
–
–
–
–
–
–
–
–
–
–
–
–
1M
–
–
–
–
–
–
–
–
–
–
–
–
Max. (1)
62.5 kbps
UBRRn = 0, Error = 0.0%
125 kbps
115.2 kbps
230.4 Kbps
125 kpbs
250 kbps
1.
195
4250E–CAN–12/04
ATMEL [ ATMEL ]
