ATmega8(L)
Alternate Functions of
Port D
The Port D pins with alternate functions are shown in
Table 28.
Port D Pins Alternate Functions
Port Pin
PD7
PD6
PD5
PD4
PD3
PD2
PD1
PD0
Alternate Function
AIN1 (Analog Comparator Negative Input)
AIN0 (Analog Comparator Positive Input)
T1 (Timer/Counter 1 External Counter Input)
XCK (USART External Clock Input/Output)
T0 (Timer/Counter 0 External Counter Input)
INT1 (External Interrupt 1 Input)
INT0 (External Interrupt 0 Input)
TXD (USART Output Pin)
RXD (USART Input Pin)
The alternate pin configuration is as follows:
• AIN1 – Port D, Bit 7
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.
• AIN0 – Port D, Bit 6
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.
• T1 – Port D, Bit 5
T1, Timer/Counter1 counter source.
• XCK/T0 – Port D, Bit 4
XCK, USART external clock.
T0, Timer/Counter0 counter source.
• INT1 – Port D, Bit 3
INT1, External Interrupt source 1: The PD3 pin can serve as an external interrupt source.
• INT0 – Port D, Bit 2
INT0, External Interrupt source 0: The PD2 pin can serve as an external interrupt source.
• TXD – Port D, Bit 1
TXD, Transmit Data (Data output pin for the USART). When the USART Transmitter is enabled,
this pin is configured as an output regardless of the value of DDD1.
• RXD – Port D, Bit 0
RXD, Receive Data (Data input pin for the USART). When the USART Receiver is enabled this
pin is configured as an input regardless of the value of DDD0. When the USART forces this pin
to be an input, the pull-up can still be controlled by the PORTD0 bit.
and
relate the alternate functions of Port D to the
overriding signals shown in
63
2486AA–AVR–02/2013
ATMEL [ ATMEL CORPORATION ]
