Datasheet
61
8246A–AVR–11/09
ATtiny2313A/4313
10.2.1 Alternate Functions of Port A
The Port A pins with alternate function are shown in Table 10-3.
• Port A, Bit 0 – XTAL1/CLKI/PCINT8
• XTAL1: Chip Clock Oscillator pin 1. Used for all chip clock sources except internal
calibratable RC oscillator. When used as a clock pin, the pin can not be used as an I/O pin.
When using internal calibratable RC Oscillator as a chip clock source, PA0 serves as an
ordinary I/O pin.
• CLKI: Clock Input from an external clock source, see “External Clock” on page 25.
• PCINT8: Pin Change Interrupt source 8. The PA0 pin can serve as an external interrupt
source for pin change interrupt 1.
• Port A, Bit 1 – XTAL2/PCINT9
• XTAL2: Chip Clock Oscillator pin 2. Used as clock pin for all chip clock sources except
internal calibratable RC Oscillator and external clock. When used as a clock pin, the pin can
not be used as an I/O pin. When using internal calibratable RC Oscillator or External clock as
a Chip clock sources, PA1 serves as an ordinary I/O pin.
• PCINT9: Pin Change Interrupt source 9. The PA1 pin can serve as an external interrupt
source for pin change interrupt 1.
• Port A, Bit 2 – RESET
/dW/PCINT10
• RESET
: External Reset input is active low and enabled by unprogramming (“1”) the
RSTDISBL Fuse. Pullup is activated and output driver and digital input are deactivated when
the pin is used as the RESET
pin.
• dW: When the debugWIRE Enable (DWEN) Fuse is programmed and Lock bits are
unprogrammed, the debugWIRE system within the target device is activated. The RESET
port pin is configured as a wire-AND (open-drain) bi-directional I/O pin with pull-up enabled
and becomes the communication gateway between target and emulator.
• PCINT10: Pin Change Interrupt source 10. The PA2 pin can serve as an external interrupt
source for pin change interrupt 1.
Table 10-3. Port A Pins Alternate Functions
Port Pin Alternate Function
PA0
XTAL1: Crystal Oscillator Input
CLKI: External Clock Input
PCINT8: Pin Change Interrupt 1, Source 8
PA1
XTAL2: Crystal Oscillator Output
PCINT9: Pin Change Interrupt 1, Source 9
PA2
RESET: Reset pin
dW: debugWire I/O
PCINT10:Pin Change Interrupt 1, Source 10