User Manual

4
ATmega48A/PA/88A/PA/168A/PA/328/P [DATASHEET]
8271E–AVR–07/2012
1.1.6 Port D (PD7:0)
Port D is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port D output buf-
fers 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.
The various special features of Port D are elaborated in ”Alternate Functions of Port D” on page 89.
1.1.7 AV
CC
AV
CC
is the supply voltage pin for the A/D Converter, PC3:0, and ADC7:6. It should be externally connected to V
CC
,
even if the ADC is not used. If the ADC is used, it should be connected to V
CC
through a low-pass filter. Note that
PC6...4 use digital supply voltage, V
CC
.
1.1.8 AREF
AREF is the analog reference pin for the A/D Converter.
1.1.9 ADC7:6 (TQFP and QFN/MLF Package Only)
In the TQFP and QFN/MLF package, ADC7:6 serve as analog inputs to the A/D converter. These pins are powered
from the analog supply and serve as 10-bit ADC channels.