65
8006K–AVR–10/10
ATtiny24/44/84
10.2.2
Alternate Functions of Port B
The Port B pins with alternate function are shown in
Table 10-7. Port B, Bit 0 – XTAL1/PCINT8
XTAL1: Chip Clock Oscillator pin 1. Used for all chip clock sources except internal
calibrateble 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, PB0 serves as an
ordinary I/O pin.
PCINT8: Pin Change Interrupt source 8. The PB0 pin can serve as an external interrupt
source for pin change interrupt 1.
Port B, Bit 1 – XTAL2/PCINT9
XTAL2: Chip Clock Oscillator pin 2. Used as clock pin for all chip clock sources except
internal calibrateble 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, PB1 serves as an ordinary I/O pin.
PCINT9: Pin Change Interrupt source 9. The PB1 pin can serve as an external interrupt
source for pin change interrupt 1.
Port B, Bit 2 – INT0/OC0A/CKOUT/PCINT10
INT0: External Interrupt Request 0.
OC0A: Output Compare Match output: The PB2 pin can serve as an external output for the
Timer/Counter0 Compare Match A. The PB2 pin has to be configured as an output (DDB2
set (one)) to serve this function. The OC0A pin is also the output pin for the PWM mode timer
function.
CKOUT - System Clock Output: The system clock can be output on the PB2 pin. The system
clock will be output if the CKOUT Fuse is programmed, regardless of the PORTB2 and DDB2
settings. It will also be output during reset.
PCINT10: Pin Change Interrupt source 10. The PB2 pin can serve as an external interrupt
source for pin change interrupt 1.
Table 10-7.
Port B Pins Alternate Functions
Port Pin
Alternate Function
PB0
XTAL1: Crystal Oscillator Input
PCINT8: Pin Change Interrupt 1, Source 8
CLKI:
External Clock Input
PB1
XTAL2: Crystal Oscillator Output
PCINT9: Pin Change Interrupt 1, Source 9
PB2
INT0:
External Interrupt 0 Input
OC0A:
Timer/Counter0 Compare Match A output
CKOUT: System Clock Output
PCINT10:Pin Change Interrupt 1, Source 10
PB3
RESET: Reset pin
dW:
debugWire I/O
PCINT11:Pin Change Interrupt 1, Source 11.