Datasheet
7
8272CS–AVR–06/11
ATmega164A/PA/324A/PA/644A/PA/1284/P
2.2 Comparison Between ATmega164A, ATmega164PA, ATmega324A, ATmega324PA,
ATmega644A, ATmega644PA, ATmega1284 and ATmega1284P
2.3 Pin Descriptions
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.
Port A also serves the functions of various special features of the
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.
Port B also serves the functions of various special features of the
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 16 K 512 1 K
bytes
ATmega164PA 16 K 512 1 K
ATmega324A 32 K 1 K 2 K
ATmega324PA 32 K 1 K 2 K
ATmega644A 64 K 2 K 4 K
ATmega644PA 64 K 2 K 4 K
ATmega1284 128 K 4 K 16 K
ATmega1284P 128 K 4 K 16 K