AT91RM3400-DK Atmel, AT91RM3400-DK Datasheet - Page 273

• Manufacturer Part Number: AT91RM3400-DK
• Description: KIT DEV FOR AT91RM3400
• Manufacturer: Atmel
• Series: AT91SAM Smart ARMr
• Type: MCUr

Specifications of AT91RM3400-DK

• Contents: Evaluation Board, Software and Documentation
• Processor To Be Evaluated: AT91RM3400
• Data Bus Width: 32 bit
• Interface Type: RS-232, USB
• For Use With/related Products: AT91RM3400
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Baud Rate in
Synchronous Mode
Baud Rate in ISO 7816
Mode
1790A–ATARM–11/03
Table 44. Baud Rate Example (OVER = 0) (Continued)
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%.
If the USART is programmed to operate in synchronous mode, the selected clock is simply
divided by the field CD in US_BRGR.
In synchronous mode, if the external clock is selected (USCLKS = 3), the clock is provided
directly by the signal on the USART SCK pin. No division is active. The value written in
US_BRGR has no effect. The external clock frequency must be at least 4.5 times lower than
the system clock.
When either the external clock SCK or the internal clock divided (MCK/DIV) is selected, the
value programmed in CD must be even if the user has to ensure a 50:50 mark/space ratio on
the SCK pin. If the internal clock MCK is selected, the Baud Rate Generator ensures a 50:50
duty cycle on the SCK pin, even if the value programmed in CD is odd.
The ISO7816 specification defines the bit rate with the following formula:
where:
•
•
•
•
BaudRate
Error
BaudRate
Source Clock
18 432 000
24 000 000
24 576 000
25 000 000
32 000 000
32 768 000
33 000 000
40 000 000
50 000 000
60 000 000
70 000 000
B is the bit rate
Di is the bit-rate adjustment factor
Fi is the clock frequency division factor
f is the ISO7816 clock frequency (Hz)
B
=
=
1
Di
----- -
Fi
=
–
=
SelectedClock
------------------------------------- -
ExpectedBaudRate
-------------------------------------------------- -
f
MCK CD 16
ActualBaudRate
CD
Baud Rate
Expected
38 400
38 400
38 400
38 400
38 400
38 400
38 400
38 400
38 400
38 400
38 400
Calculation
Result
113.93
30.00
39.06
40.00
40.69
52.08
53.33
53.71
65.10
81.38
97.66
114
CD
30
39
40
40
52
53
54
65
81
98
Baud Rate
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
38 377.19
Actual
AT91RM3400
0.00%
0.16%
0.00%
0.76%
0.16%
0.63%
0.54%
0.16%
0.47%
0.35%
0.06%
Error
273