Datasheet

ATtiny25/45/85 [DATASHEET]

2586Q–AVR–08/2013

• Port B, Bit 4 – XTAL2/CLKO/ADC2/OC1B/PCINT4

• 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, PB4 serves as an ordinary I/O pin.

• CLKO: The devided system clock can be output on the pin PB4. The divided system clock will be output if the

CKOUT Fuse is programmed, regardless of the PORTB4 and DDB4 settings. It will also be output during reset.

• ADC2: Analog to Digital Converter, Channel 2

• OC1B: Output Compare Match output: The PB4 pin can serve as an external output for the Timer/Counter1

Compare Match B when configured as an output (DDB4 set). The OC1B pin is also the output pin for the PWM

mode timer function.

• PCINT4: Pin Change Interrupt source 4.

• Port B, Bit 3 – XTAL1/CLKI/ADC3/OC1B

/PCINT3

• 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.

• CLKI: Clock Input from an external clock source, see “External Clock” on page 26.

• ADC3: Analog to Digital Converter, Channel 3

•OC1B: Inverted Output Compare Match output: The PB3 pin can serve as an external output for the

Timer/Counter1 Compare Match B when configured as an output (DDB3 set). The OC1B

pin is also the inverted

output pin for the PWM mode timer function.

• PCINT3: Pin Change Interrupt source 3.

• Port B, Bit 2 – SCK/ADC1/T0/USCK/SCL/INT0/PCINT2

• SCK: Master Clock output, Slave Clock input pin for SPI channel. When the SPI is enabled as a Slave, this pin

is configured as an input regardless of the setting of DDB2. When the SPI is enabled as a Master, the data

direction of this pin is controlled by DDPB2. When the pin is forced by the SPI to be an input, the pull-up can still

be controlled by the PORTB2 bit.

• ADC1: Analog to Digital Converter, Channel 1

• T0: Timer/Counter0 counter source.

• USCK: Three-wire mode Universal Serial Interface Clock.

• SCL: Two-wire mode Serial Clock for USI Two-wire mode.

• INT0: External Interrupt source 0.

• PCINT2: Pin Change Interrupt source 2.

• Port B, Bit 1 – MISO/AIN1/OC0B/OC1A/DO/PCINT1

• MISO: Master Data input, Slave Data output pin for SPI channel. When the SPI is enabled as a Master, this pin

is configured as an input regardless of the setting of DDB1. When the SPI is enabled as a Slave, the data

direction of this pin is controlled by DDB1. When the pin is forced by the SPI to be an input, the pull-up can still

be controlled by the PORTB1 bit.

• AIN1: Analog Comparator Negative Input. Configure the port pin as input with the internal pull-up switched off to

avoid the digital port function from interfering with the function of the Analog Comparator.

• OC0B: Output Compare Match output. The PB1 pin can serve as an external output for the Timer/Counter0

Compare Match B. The PB1 pin has to be configured as an output (DDB1 set (one)) to serve this function. The

OC0B pin is also the output pin for the PWM mode timer function.