at91rm3400 ATMEL Corporation, at91rm3400 Datasheet - Page 270

• Manufacturer Part Number: at91rm3400
• Description: Atmel Advanced At91 Arm Microcontroller
• Manufacturer: ATMEL Corporation

Product Dependencies
I/O Lines
Power
Management
Interrupt
270
AT91RM3400
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.
All the pins of the modems may or may not not be implemented on the USART within a prod-
uct. Frequently, only the USART1 is fully equipped with all the modem signals. For the other
USARTs of the product 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 applica-
tion 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 Inter-
rupt 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.
1790A–ATARM–11/03