ATtiny45 datasheet(54/196 Pages) ATMEL

54 / 196 page

7598H–AVR–07/09

ATtiny25/45/85

10.3.1

MCU Control Register – MCUCR

• Bit 6 – PUD: Pull-up Disable

When this bit is written to one, the pull-ups in the I/O ports are disabled even if the DDxn and

PORTxn Registers are configured to enable the pull-ups ({DDxn, PORTxn} = 0b01). See “Con-

figuring the Pin” on page 48 for more details about this feature.

10.3.2

Alternate Functions of Port B

The Port B pins with alternate function are shown in Table 10-3.

Notes:

1. Reset Pin, debugWIRE I/O, ADC Input Channel or Pin Change Interrupt.

2. XOSC Output, Divided System Clock Output, ADC Input Channel, Timer/Counter1 Output

Compare and PWM Output B, or Pin Change Interrupt.

3. XOSC Input / External Clock Input, ADC Input Channel, Timer/Counter1 Inverted Output Com-

pare and PWM Output B, or Pin Change Interrupt.

4. Serial Clock Input, ADC Input Channel, Timer/Counter Clock Input, USI Clock (three-wire

mode), USI Clock (two-wire mode), External Interrupt, or Pin Change Interrupt.

5. Serial Data Input, Analog Comparator Negative Input, Timer/Counter0 Output Compare and

PWM Output B, Timer/Counter1 Output Compare and PWM Output A, USI Data Output

(three-wire mode), or Pin Change Interrupt.

6. Serial Data Output, Analog Comparator Positive Input, Timer/Counter0 Output Compare and

PWM Output A, Timer/Counter1 Inverted Output Compare and PWM Output A, USI Data Input

(three-wire mode), USI Data (two-wire mode), Voltage Ref., or Pin Change Interrupt.

• Port B, Bit 5 - RESET/dW/ADC0/PCINT5

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 unpro-

grammed, 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.

ADC0: Analog to Digital Converter, Channel 0.

PCINT5: Pin Change Interrupt source 5.

Bit

BODS

PUD

SM1

SM0

BODSE

ISC01

ISC00

MCUCR

Read/Write

R/W

Initial Value

Table 10-3.

Port B Pins Alternate Functions

Port Pin

Alternate Function

PB5

RESET / dW / ADC0 / PCINT5(1)

PB4

XTAL2 / CLKO / ADC2 / OC1B / PCINT4(2)

PB3

XTAL1 / ADC3 / OC1B / PCINT3(3)

PB2

SCK / ADC1 / T0 / USCK / SCL / INT0 / PCINT2(4)

PB1

MISO / AIN1 / OC0B / OC1A / DO / PCINT1(5)

PB0

MOSI / AIN0 / OC0A / OC1A / DI / SDA / AREF / PCINT0(6)

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