Atmel Xplained Pro Evaluation Kit ATSAM4E-XPRO ATSAM4E-XPRO Fiche De Données
Codes de produits
ATSAM4E-XPRO
SAM4E [DATASHEET]
Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14
892
The modified architecture is presented below:
Figure 38-4.
Fractional Baud Rate Generator
38.7.1.3 Baud Rate in Synchronous Mode or SPI Mode
If the USART is programmed to operate in synchronous mode, the selected clock is simply divided by the field CD
in the US_BRGR.
in the 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 3 times lower than the system clock. In synchronous mode master (USCLKS = 0 or 1,
CLK0 set to 1), the receive part limits the SCK maximum frequency tof
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 3 times lower than the system clock. In synchronous mode master (USCLKS = 0 or 1,
CLK0 set to 1), the receive part limits the SCK maximum frequency tof
peripheral clock
/3 in USART mode, or f
peripheral
clock
/6 in SPI mode.
When either the external clock SCK or the internal clock divided (peripheral clock/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. When the
peripheral clock 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.
programmed in CD must be even if the user has to ensure a 50:50 mark/space ratio on the SCK pin. When the
peripheral clock 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.
38.7.1.4 Baud Rate in ISO 7816 Mode
The ISO7816 specification defines the bit rate with the following formula:
where:
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)
Baudrate
SelectedClock
8 2
Over
–
(
) CD
FP
8
-------
+
----------------------------------------------------------------
=
MCK/DIV
16-bit Counter
0
Baud Rate
Clock
CD
CD
Sampling
Divider
0
1
>1
Sampling
Clock
Reserved
MCK
SCK
USCLKS
OVER
SCK
SYNC
SYNC
USCLKS = 3
1
0
2
3
0
1
0
1
FIDI
Glitch-free
Logic
Modulus
Control
FP
FP
BaudRate
SelectedClock
CD
--------------------------------------
=
B
Di
Fi
------
f
×
=