ATMEGA8_14 Datasheet, PDF (63/331 Pages) ATMEL Corporation – High-performance, Low-power Atmel

ATmega8(L)
Alternate Functions of The Port D pins with alternate functions are shown in Table 28.
Port D
Table 28. Port D Pins Alternate Functions
Port Pin
Alternate Function
PD7
AIN1 (Analog Comparator Negative Input)
PD6
AIN0 (Analog Comparator Positive Input)
PD5
T1 (Timer/Counter 1 External Counter Input)
PD4
XCK (USART External Clock Input/Output)
T0 (Timer/Counter 0 External Counter Input)
PD3
INT1 (External Interrupt 1 Input)
PD2
INT0 (External Interrupt 0 Input)
PD1
TXD (USART Output Pin)
PD0
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.
Table 29 on page 64 and Table 30 on page 64 relate the alternate functions of Port D to the
overriding signals shown in Figure 25 on page 56.
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