Atmega128(l) – Rainbow Electronics ATmega128L User Manual
Page 74
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ATmega128(L)
2467B–09/01
• IC1 - Port D, Bit 4
IC1 - In put Ca pture Pin1 : Th e PD4 pin ca n a ct as a n inp ut ca ptu re pin for
Timer/Counter1.
• 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 configured 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, 2-wire Serial Interface Data: When the TWEN bit in TWCR is set (one) to enable
the 2-wire Serial Interface, pin PD1 is disconnected from the port and becomes the
Serial Data I/O pin for the 2-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, 2-wire Serial Interface Clock: When the TWEN bit in TWCR is set (one) to enable
the 2-wire Serial Interface, pin PD0 is disconnected from the port and becomes the
Serial Clock I/O pin for the 2-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.
Table 37 and Table 38 relates the alternate functions of Port D to the overriding signals
shown in