ATMEGA8U2_14 Datasheet, PDF (75/310 Pages) ATMEL Corporation – 125 Powerful Instructions – Most Single Clock Cycle Execution

ATmega8U2/16U2/32U2
• PDI/MOSI/PCINT2 – Port B, Bit 2
PDI, SPI Serial Programming Data Input. During Serial Program Downloading, this pin is used
as data input line for the AT90USB82/162.
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 DDB2. When the SPI is
enabled as a master, the data direction of this pin is controlled by DDB2. When the pin is forced
to be an input, the pull-up can still be controlled by the PORTB2 bit.
PCINT2, Pin Change Interrupt source 2: The PB2 pin can serve as an external interrupt source.
• SCK/PCINT1 – Port B, Bit 1
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 DDB1. When the SPI0 is
enabled as a master, the data direction of this pin is controlled by DDB1. When the pin is forced
to be an input, the pull-up can still be controlled by the PORTB1 bit. This pin also serves as
Clock for the Serial Programming interface.
PCINT1, Pin Change Interrupt source 1: The PB1 pin can serve as an external interrupt source.
• SS/PCINT0 – Port B, Bit 0
SS: Slave Port Select input. When the SPI is enabled as a slave, this pin is configured as an
input regardless of the setting of DDB0. 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 DDB0.
When the pin is forced to be an input, the pull-up can still be controlled by the PORTB0 bit.
PCINT0, Pin Change Interrupt source 0: The PB0 pin can serve as an external interrupt source.
Table 12-4 and Table 12-5 relate the alternate functions of Port B to the overriding signals
shown in Figure 12-5 on page 72. SPI MSTR INPUT and SPI SLAVE OUTPUT constitute the
MISO signal, while MOSI is divided into SPI MSTR OUTPUT and SPI SLAVE INPUT.
PCINT0, Pin Change Interrupt source 0: The PB0 pin can serve as an external interrupt source
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