ATMEGA329P_07 Datasheet, PDF (6/24 Pages) ATMEL Corporation – 8-bit Microcontroller with 32K Bytes In-System Programmable Flash

2.3 Pin Descriptions
2.3.1
V_CC
2.3.2 GND
The following section describes the I/O-pin special functions.
Digital supply voltage.
2.3.3
Ground.
Port A (PA7..PA0)
2.3.4
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 ATmega329P/3290P as listed
on page 72.
Port B (PB7..PB0)
2.3.5
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 ATmega329P/3290P as listed
on page 73.
Port C (PC7..PC0)
2.3.6
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 ATmega329P/3290P as listed on page
76.
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 ATmega329P/3290P as listed
on page 77.
6 ATmega329P/3290P
8021CS–AVR–08/07