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ATmega64A [DATASHEET]
8160D–AVR–02/2013
INT3/TXD1 – Port D, Bit 3
INT3, External Interrupt Source 3: The PD3 pin can serve as an External Interrupt source to the MCU.
TXD1, Transmit Data (Data output pin for the USART1). When the USART1 transmitter is enabled, this pin is con-
figured as an output regardless of the value of DDD3.
INT2/RXD1 – Port D, Bit 2
INT2, External Interrupt source 2. The PD2 pin can serve as an External Interrupt source to the MCU.
RXD1, Receive Data (Data input pin for the USART1). When the USART1 receiver is enabled this pin is configured
as an input regardless of the value of DDD2. When the USART forces this pin to be an input, the pull-up can still be
controlled by the PORTD2 bit.
INT1/SDA – Port D, Bit 1
INT1, External Interrupt Source 1. The PD1 pin can serve as an External Interrupt source to the MCU.
SDA, Two-wire Serial Interface Data: When the TWEN bit in TWCR is set (one) to enable the Two-wire Serial Inter-
face, pin PD1 is disconnected from the port and becomes the serial data I/O pin for the Two-wire Serial Interface.
In this mode, there is a spike filter on the pin to suppress spikes shorter than 50 ns on the input signal, and the pin
is driven by an open drain driver with slew-rate limitation.
INT0/SCL – Port D, Bit 0
INT0, External Interrupt Source 0. The PD0 pin can serve as an External Interrupt source to the MCU.
SCL, Two-wire Serial Interface Clock: When the TWEN bit in TWCR is set (one) to enable the Two-wire Serial
Interface, pin PD0 is disconnected from the port and becomes the serial clock I/O pin for the Two-wire Serial Inter-
face. In this mode, there is a spike filter on the pin to suppress spikes shorter than 50 ns on the input signal, and
the pin is driven by an open drain driver with slew-rate limitation.