Datasheet

773
SAM3X / SAM3A [DATASHEET]
Atmel-11057C-ATARM-SAM3X-SAM3A-Datasheet_23-Mar-15
35.6 Product Dependencies
35.6.1 I/O Lines
The pins used for interfacing the USART may be multiplexed with the PIO lines. The programmer 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 is used, the internal pull up on TXD must also be enabled.
35.6.2 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 35-3. I/O Lines
Instance Signal I/O Line Peripheral
USART0 CTS0 PB26 A
USART0 RTS0 PB25 A
USART0 RXD0 PA10 A
USART0 SCK0 PA17 B
USART0 TXD0 PA11 A
USART1 CTS1 PA15 A
USART1 RTS1 PA14 A
USART1 RXD1 PA12 A
USART1 SCK1 PA16 A
USART1 TXD1 PA13 A
USART2 CTS2 PB23 A
USART2 RTS2 PB22 A
USART2 RXD2 PB21 A
USART2 SCK2 PB24 A
USART2 TXD2 PB20 A
USART3 CTS3 PF4 A
USART3 RTS3 PF5 A
USART3 RXD3 PD5 B
USART3 SCK3 PE16 B
USART3 TXD3 PD4 B