SAM7X256_14 Datasheet, PDF (294/662 Pages) ATMEL Corporation – ARM-based Flash MCU

30.5 Product Dependencies
30.5.1 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 is 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.
30.5.2 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.
30.5.3 Interrupt
The USART interrupt line is connected on one of the internal sources of the Advanced Interrupt Controller. Using the
USART interrupt requires the AIC to be programmed first. Note that it is not recommended to use the USART interrupt
line in edge sensitive mode.
SAM7X Series [DATASHEET]
6120K–ATARM–11-Feb-14
294