ATMEGA649P_14 Datasheet, PDF (9/39 Pages) ATMEL Corporation – 8-bit Atmel Microcontroller with 16/32/64KB In-System Programmable Flash

2.3 Pin descriptions
The following section describes the I/O-pin special functions.
2.3.1 V_CC
Digital supply voltage.
2.3.2 GND
Ground.
2.3.3
Port A (PA7...PA0)
Port A is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port A output
buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port A pins that
are externally pulled low will source current if the pull-up resistors are activated. The Port A pins are tri-stated when
a reset condition becomes active, even if the clock is not running.
Port A also serves the functions of various special features of the Atmel
ATmega169A/169PA/329A/329PA/3290A/3290PA/649A/649P/6490A/6490P as listed on page 72.
2.3.4
Port B (PB7...PB0)
Port B is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port B output
buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port B pins that
are externally pulled low will source current if the pull-up resistors are activated. The Port B pins are tri-stated when
a reset condition becomes active, even if the clock is not running.
Port B has better driving capabilities than the other ports.
Port B also serves the functions of various special features of the
ATmega169A/169PA/329A/329PA/3290A/3290PA/649A/649P/6490A/6490P as listed on page 73.
2.3.5
Port C (PC7...PC0)
Port C is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port C output
buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port C pins that
are externally pulled low will source current if the pull-up resistors are activated. The Port C pins are tri-stated when
a reset condition becomes active, even if the clock is not running.
Port C also serves the functions of special features of the
ATmega169A/169PA/329A/329PA/3290A/3290PA/649A/649P/6490A/6490P as listed on page 76.
2.3.6
Port D (PD7...PD0)
Port D is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port D output
buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port D pins that
are externally pulled low will source current if the pull-up resistors are activated. The Port D pins are tri-stated when
a reset condition becomes active, even if the clock is not running.
Port D also serves the functions of various special features of the
ATmega169A/169PA/329A/329PA/3290A/3290PA/649A/649P/6490A/6490P as listed on page 77.
2.3.7
Port E (PE7...PE0)
Port E is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port E output
buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port E pins that
ATmega169A/PA/329A/PA/649A/P/3290A/PA/6490A/P [DATASHEET SUMMARY]
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8284FS–AVR–07/2014