Atmel SAM4S Series, Preliminary Data Sheet

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11100B–ATARM–31-Jul-12
SAM4S Series [Preliminary]
34.6 Product Dependencies
34.6.1 I/O Lines
The pins used for interfacing the USART may be multiplexed with the PIO lines. The program-
mer must first program the PIO controller to assign the desired USART pins to their peripheral
function. If I/O lines of the USART are not used by the application, they can be used for other
purposes by the PIO Controller.
To prevent the TXD line from falling when the USART is disabled, the use of an internal pull up
is mandatory. If the hardware handshaking feature or Modem mode is used, the internal pull up
on TXD must also be enabled.All the pins of the modems may or may not be implemented on
the USART. Only USART1 fully equipped with all the modem signals. On USARTs not equipped
with the corresponding pin, the associated control bits and statuses have no effect on the behav-
ior of the USART.
34.6.2 Power Management
The USART is not continuously clocked. The programmer must first enable the USART Clock in
the Power Management Controller (PMC) before using the USART. However, if the application
does not require USART operations, the USART clock can be stopped when not needed and be
restarted later. In this case, the USART will resume its operations where it left off.
Configuring the USART does not require the USART clock to be enabled.
Table 34-3. I/O Lines
Instance Signal I/O Line Peripheral
USART0 CTS0 PA8 A
USART0 RTS0 PA7 A
USART0 RXD0 PA5 A
USART0 SCK0 PA2 B
USART0 TXD0 PA6 A
USART1 CTS1 PA25 A
USART1 DCD1 PA26 A
USART1 DSR1 PA28 A
USART1 DTR1 PA27 A
USART1 RI1 PA29 A
USART1 RTS1 PA24 A
USART1 RXD1 PA21 A
USART1 SCK1 PA23 A
USART1 TXD1 PA22 A