AT32UC3A3256S_2 Datasheet, PDF (548/1014 Pages) ATMEL Corporation – 32-bit AVR®Microcontroller

AT32UC3A3/A4
The following formula performs the calculation of the Baud Rate.
Baudrate = ₍---₈-^S---₍^e--₂-^l--^e--–-^c---^tO--^e---_vd---_e-^C--_r--^l-₎-^o-_C--^c---_Dk----₎-
This gives a maximum baud rate of CLK_USART divided by 8, assuming that CLK_USART is
the highest possible clock and that OVER is programmed at 1.
25.6.1.2
Baud Rate Calculation Example
Table 25-3 shows calculations of CD to obtain a baud rate at 38400 bauds for different source
clock frequencies. This table also shows the actual resulting baud rate and the error.
Table 25-3. Baud Rate Example (OVER = 0)
Expected Baud
Source Clock
Rate
Calculation Result
CD
MHz
Bit/s
3 686 400
38 400
6.00
6
4 915 200
38 400
8.00
8
5 000 000
38 400
8.14
8
7 372 800
38 400
12.00
12
8 000 000
38 400
13.02
13
12 000 000
38 400
19.53
20
12 288 000
38 400
20.00
20
14 318 180
38 400
23.30
23
14 745 600
38 400
24.00
24
18 432 000
38 400
30.00
30
24 000 000
38 400
39.06
39
24 576 000
38 400
40.00
40
25 000 000
38 400
40.69
40
32 000 000
38 400
52.08
52
32 768 000
38 400
53.33
53
33 000 000
38 400
53.71
54
40 000 000
38 400
65.10
65
50 000 000
38 400
81.38
81
60 000 000
38 400
97.66
98
Actual Baud Rate
Bit/s
38 400.00
38 400.00
39 062.50
38 400.00
38 461.54
37 500.00
38 400.00
38 908.10
38 400.00
38 400.00
38 461.54
38 400.00
38 109.76
38 461.54
38 641.51
38 194.44
38 461.54
38 580.25
38 265.31
Error
0.00%
0.00%
1.70%
0.00%
0.16%
2.40%
0.00%
1.31%
0.00%
0.00%
0.16%
0.00%
0.76%
0.16%
0.63%
0.54%
0.16%
0.47%
0.35%
The baud rate is calculated with the following formula:
BaudRate = (CLKUSART) ⁄ (CD × 16)
The baud rate error is calculated with the following formula. It is not recommended to work with
an error higher than 5%.
32072C–AVR32–2010/03
548