at91sam9263 ATMEL Corporation, at91sam9263 Datasheet - Page 512

• Manufacturer Part Number: at91sam9263
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

Figure 33-3. Baud Rate Generator
33.6.1.1
33.6.1.2
Table 33-2.
6249D–ATARM–20-Dec-07
Source Clock
12 000 000
12 288 000
3 686 400
4 915 200
5 000 000
7 372 800
8 000 000
MHz
Baud Rate in Asynchronous Mode
Baud Rate Calculation Example
SCK
Baud Rate Example (OVER = 0)
Reserved
MCK/DIV
MCK
Expected Baud
If the USART is programmed to operate in asynchronous mode, the selected clock is first
divided by CD, which is field programmed in the Baud Rate Generator Register (US_BRGR).
The resulting clock is provided to the receiver as a sampling clock and then divided by 16 or 8,
depending on the programming of the OVER bit in US_MR.
If OVER is set to 1, the receiver sampling is 8 times higher than the baud rate clock. If OVER is
cleared, the sampling is performed at 16 times the baud rate clock.
The following formula performs the calculation of the Baud Rate.
This gives a maximum baud rate of MCK divided by 8, assuming that MCK is the highest possi-
ble clock and that OVER is programmed at 1.
Table 33-2
clock frequencies. This table also shows the actual resulting baud rate and the error.
USCLKS
0
1
2
3
38 400
38 400
38 400
38 400
38 400
38 400
38 400
Rate
Bit/s
Baudrate
shows calculations of CD to obtain a baud rate at 38400 bauds for different source
16-bit Counter
=
Calculation Result
--------------------------------------------
(
8 2 Over
SelectedClock
CD
(
–
12.00
13.02
19.53
20.00
6.00
8.00
8.14
USCLKS = 3
)CD
0
SYNC
)
CD
>1
1
0
CD
12
13
20
20
6
8
8
1
0
AT91SAM9263 Preliminary
OVER
Sampling
Divider
Actual Baud Rate
FIDI
38 400.00
38 400.00
39 062.50
38 400.00
38 461.54
37 500.00
38 400.00
Bit/s
0
1
SYNC
SCK
Baud Rate
Sampling
Clock
Clock
0.00%
0.00%
1.70%
0.00%
0.16%
2.40%
0.00%
Error
512