Datasheet

569
32117D–AVR-01/12
AT32UC3C
The following formula performs the calculation of the Baud Rate.
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.
The baud rate is calculated with the following formula:
The baud rate error is calculated with the following formula. It is not recommended to work with
an error higher than 5%.
Baudrate
SelectedClock
82 Over–()CD()
--------------------------------------------=
Table 25-3. Baud Rate Example (OVER = 0)
Source Clock
Expected Baud
Rate Calculation Result CD Actual Baud Rate Error
MHz Bit/s Bit/s
3 686 400 38 400 6.00 6 38 400.00 0.00%
4 915 200 38 400 8.00 8 38 400.00 0.00%
5 000 000 38 400 8.14 8 39 062.50 1.70%
7 372 800 38 400 12.00 12 38 400.00 0.00%
8 000 000 38 400 13.02 13 38 461.54 0.16%
12 000 000 38 400 19.53 20 37 500.00 2.40%
12 288 000 38 400 20.00 20 38 400.00 0.00%
14 318 180 38 400 23.30 23 38 908.10 1.31%
14 745 600 38 400 24.00 24 38 400.00 0.00%
18 432 000 38 400 30.00 30 38 400.00 0.00%
24 000 000 38 400 39.06 39 38 461.54 0.16%
24 576 000 38 400 40.00 40 38 400.00 0.00%
25 000 000 38 400 40.69 40 38 109.76 0.76%
32 000 000 38 400 52.08 52 38 461.54 0.16%
32 768 000 38 400 53.33 53 38 641.51 0.63%
33 000 000 38 400 53.71 54 38 194.44 0.54%
40 000 000 38 400 65.10 65 38 461.54 0.16%
50 000 000 38 400 81.38 81 38 580.25 0.47%
60 000 000 38 400 97.66 98 38 265.31 0.35%
BaudRate CLKUSART()CD 16×()⁄=