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
78.
2.3.7
AVCC
AVCC is the supply voltage pin for the A/D Converter, PC3..0, and ADC7..6. It should be exter-
nally connected to VCC, even if the ADC is not used. If the ADC is used, it should be connected
to VCC through a low-pass filter. Note that PC6..4 use digital supply voltage, VCC
.
2.3.8
2.3.9
AREF
AREF is the analog reference pin for the A/D Converter.
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.
3. About Code Examples
This documentation contains simple code examples that briefly show how to use various parts of
the device. These code examples assume that the part specific header file is included before
compilation. Be aware that not all C compiler vendors include bit definitions in the header files
and interrupt handling in C is compiler dependent. Please confirm with the C compiler documen-
tation for more details.
For I/O Registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”, and “SBI”
instructions must be replaced with instructions that allow access to extended I/O. Typically
“LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and “CBR”.
6
ATmega48/88/168
2545E–AVR–02/05
MICROCHIP [ MICROCHIP ]
