Datasheet

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MOSI: SPI Master Data output, Slave Data input for SPI channel. When the SPI is enabled as a Slave,

this pin is configured as an input regardless of the setting of DDB3. When the SPI is enabled as a Master,

the data direction of this pin is controlled by DDB3. When the pin is forced by the SPI to be an input, the

pull-up can still be controlled by the PORTB3 bit.

OC2, Output Compare Match Output: The PB3 pin can serve as an external output for the Timer/

Counter2 Compare Match. The PB3 pin has to be configured as an output (DDB3 set (one)) to serve this

function. The OC2 pin is also the output pin for the PWM mode timer function.

• SS/OC1B – Port B, Bit 2

SS: Slave Select input. When the SPI is enabled as a Slave, this pin is configured as an input regardless

of the setting of DDB2. As a Slave, the SPI is activated when this pin is driven low. When the SPI is

enabled as a Master, the data direction of this pin is controlled by DDB2. When the pin is forced by the

SPI to be an input, the pull-up can still be controlled by the PORTB2 bit.

OC1B, Output Compare Match output: The PB2 pin can serve as an external output for the Timer/

Counter1 Compare Match B. The PB2 pin has to be configured as an output (DDB2 set (one)) to serve

this function. The OC1B pin is also the output pin for the PWM mode timer function.

• OC1A – Port B, Bit 1

OC1A, Output Compare Match output: The PB1 pin can serve as an external output for the Timer/

Counter1 Compare Match A. The PB1 pin has to be configured as an output (DDB1 set (one)) to serve

this function. The OC1A pin is also the output pin for the PWM mode timer function.

• ICP1 – Port B, Bit 0

ICP1 – Input Capture Pin: The PB0 pin can act as an Input Capture Pin for Timer/Counter1.

The tables below relate the alternate functions of Port B to the overriding signals shown in figure Figure

18-5. SPI MSTR INPUT and SPI SLAVE OUTPUT constitute the MISO signal, while MOSI is divided into

SPI MSTR OUTPUT and SPI SLAVE INPUT.

Table 18-4. Overriding Signals for Alternate Functions in PB7:PB4

Signal

Name

PB7/XTAL2/

TOSC2

(1)(2)

PB6/XTAL1/

TOSC1

(1)

PB5/SCK PB4/MISO

PUOE EXT • (INTRC + AS2) INTRC + AS2 SPE • MSTR SPE • MSTR

PUO 0 0 PORTB5 • PUD PORTB4 • PUD

DDOE EXT • (INTRC + AS2) INTRC + AS2 SPE • MSTR SPE • MSTR

DDOV 0 0 0 0

PVOE 0 0 SPE • MSTR SPE • MSTR

PVOV 0 0 SCK OUTPUT SPI SLAVE OUTPUT

DIEOE EXT • (INTRC + AS2) INTRC + AS2 0 0

DIEOV 0 0 0 0

DI – – SCK INPUT SPI MSTR INPUT

AIO Oscillator Output Oscillator/Clock Input – –

Note:

AVR 8-Bit Microcontroller

I/O Ports

Datasheet Complete

40001974A-page 88