9

ATmega169A/PA/329A/PA/649A/P/3290A/PA/6490A/P [DATASHEET SUMMARY]

8284FS–AVR–07/2014

2.3

Pin descriptions

The following section describes the I/O-pin special functions.

2.3.1

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