7
8272E–AVR–04/2013
ATmega164A/PA/324A/PA/644A/PA/1284/P
2.2
Comparison between ATmega164A, ATmega164PA, ATmega324A, ATmega324PA,
ATmega644A, ATmega644PA, ATmega1284 and ATmega1284P
2.3
Pin Descriptions11
2.3.1
VCC
Digital supply voltage.
2.3.2
GND
Ground.
2.3.3
Port A (PA7:PA0)
Port A serves as analog inputs to the Analog-to-digital Converter.
Port A also serves as 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.
Por t A also ser v es the fu nc tio n s of va riou s sp ecial fea t ur es of the Atm e l
ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P as listed on
page 80.
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.
Por t
B
also
se rve s
the
fun c tion s
of
va riou s
sp ecial
fe atu r e s
of
th e
ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P as listed on
page 82.
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
Table 2-1.
Differences between ATmega164A, ATmega164PA, ATmega324A, ATmega324PA, ATmega644A,
ATmega644PA, ATmega1284 and ATmega1284P.
Device
Flash
EEPROM
RAM
Units
ATmega164A
16K
512
1K
bytes
ATmega164PA
16K
512
1K
ATmega324A
32K
1K
2K
ATmega324PA
32K
1K
2K
ATmega644A
64K
2K
4K
ATmega644PA
64K
2K
4K
ATmega1284
128K
4K
16K
ATmega1284P
128K
4K
16K