Atmel SAM9X25, Manual

Page: 798 / 1145

798
11054A–ATARM–27-Jul-11
SAM9X25
798
11054A–ATARM–27-Jul-11
SAM9X25
39.6 Product Dependencies
39.6.1 I/O Lines
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.
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.
39.6.2 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 39-3. I/O Lines
Instance Signal I/O Line Peripheral
USART0 CTS0 PA3 A
USART0 RTS0 PA2 A
USART0 RXD0 PA1 A
USART0 SCK0 PA4 A
USART0 TXD0 PA0 A
USART1 CTS1 PC28 C
USART1 RTS1 PC27 C
USART1 RXD1 PA6 A
USART1 SCK1 PC29 C
USART1 TXD1 PA5 A
USART2 CTS2 PB1 B
USART2 RTS2 PB0 B
USART2 RXD2 PA8 A
USART2 SCK2 PB2 B
USART2 TXD2 PA7 A
USART3 CTS3 PC25 B
USART3 RTS3 PC24 B
USART3 RXD3 PC23 B
USART3 SCK3 PC26 B
USART3 TXD3 PC22 B