at91cap7e ATMEL Corporation, at91cap7e Datasheet - Page 346

• Manufacturer Part Number: at91cap7e
• Description: Customizable Microcontroller
• Manufacturer: ATMEL Corporation

29.5
29.5.1
29.5.2
29.5.3
346
Product Dependencies
AT91CAP7E
I/O Lines
Power Management
Interrupt
The pins used for interfacing the USART are multiplexed with the PIO lines. The programmer
must first program the PIOA controller to select the USART I/O alternate functions. 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. On USARTs not
equipped with the corresponding pin, the associated control bits and statuses have no effect on
the behavior of the USART.
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.
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.
8549A–CAP–10/08