ATmega32A datasheet(60/352 Pages) ATMEL

60 / 352 page

8155B–AVR–07/09

ATmega32A

• MOSI – Port B, Bit 5

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

this pin is configured as an input regardless of the setting of DDB5. When the SPI is enabled as

a Master, the data direction of this pin is controlled by DDB5. When the pin is forced by the SPI

to be an input, the pull-up can still be controlled by the PORTB5 bit.

•SS – Port B, Bit 4

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

regardless of the setting of DDB4. 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 DDB4. When

the pin is forced by the SPI to be an input, the pull-up can still be controlled by the PORTB4 bit.

• AIN1/OC0 – Port B, Bit 3

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.

OC0, Output Compare Match output: The PB3 pin can serve as an external output for the

Timer/Counter0 Compare Match. The PB3 pin has to be configured as an output (DDB3 set

(one)) to serve this function. The OC0 pin is also the output pin for the PWM mode timer

function.

• AIN0/INT2 – Port B, Bit 2

AIN0, Analog Comparator Positive 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.

INT2, External Interrupt Source 2: The PB2 pin can serve as an external interrupt source to the

MCU.

• T1 – Port B, Bit 1

T1, Timer/Counter1 Counter Source.

• T0/XCK – Port B, Bit 0

T0, Timer/Counter0 Counter Source.

XCK, USART External Clock. The Data Direction Register (DDB0) controls whether the clock is

output (DDB0 set) or input (DDB0 cleared). The XCK pin is active only when the USART oper-

ates in Synchronous mode.

Table 12-7 and Table 12-8 relate the alternate functions of Port B to the overriding signals

shown in Figure 12-5 on page 56. SPI MSTR INPUT and SPI SLAVE OUTPUT constitute the

MISO signal, while MOSI is divided into SPI MSTR OUTPUT and SPI SLAVE INPUT.

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