Datasheet

889
SAM4E [DATASHEET]
Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14
38.6 Product Dependencies
38.6.1 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 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 behavior of the USART.
38.6.2 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.
38.6.3 Interrupt
The USART interrupt line is connected on one of the internal sources of the Interrupt Controller. Using the USART
interrupt requires the Interrupt Controller to be programmed first.
Table 38-3. I/O Lines
Instance Signal I/O Line Peripheral
USART0 CTS0 PB2 C
USART0 RTS0 PB3 C
USART0 RXD0 PB0 C
USART0 SCK0 PB13 C
USART0 TXD0 PB1 C
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
Table 38-4. Peripheral IDs
Instance ID
USART0 14
USART1 15