SAM9G25_14 Datasheet, PDF (813/1167 Pages) ATMEL Corporation – Atmel | SMART ARM-based Embedded Microprocessor

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 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 is used, the internal pull up on TXD must also be enabled.
Table 39-3. I/O Lines
Instance
USART0
USART0
USART0
USART0
USART0
USART1
USART1
USART1
USART1
USART1
USART2
USART2
USART2
USART2
USART2
USART3
USART3
USART3
USART3
USART3
Signal
CTS0
RTS0
RXD0
SCK0
TXD0
CTS1
RTS1
RXD1
SCK1
TXD1
CTS2
RTS2
RXD2
SCK2
TXD2
CTS3
RTS3
RXD3
SCK3
TXD3
I/O Line
PA3
PA2
PA1
PA4
PA0
PC28
PC27
PA6
PC29
PA5
PB1
PB0
PA8
PB2
PA7
PC25
PC24
PC23
PC26
PC22
Peripheral
A
A
A
A
A
C
C
A
C
A
B
B
A
B
A
B
B
B
B
B
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.
SAM9G25 [DATASHEET]
Atmel-11032E-ATARM-SAMG25-Datasheet_13-Oct-14
1813