6.1.2. GND
Ground.
6.1.3. Port A (PA7:PA0)
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 tristated 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 ATmega64A as listed in Alternate
Functions of Port A.
6.1.4. 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 tristated 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 ATmega64A as listed in Alternate
Functions of Port B.
6.1.5. 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 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 tristated when a reset condition becomes active, even if the clock is not running.
Port C also serves the functions of special features of the ATmega64A as listed in Alternate Functions of
Port C. In ATmega103 compatibility mode, Port C is output only, and the port C pins are not tri-stated
when a reset condition becomes active.
Note: The Atmel AVR ATmega64A is by default shipped in ATmega103 compatibility mode. Thus, if the
parts are not programmed before they are put on the PCB, PORTC will be output during first power up,
and until the ATmega103 compatibility mode is disabled.
6.1.6. 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 tristated 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 ATmega64A as listed in Alternate
Functions of Port D.
6.1.7. Port E (PE7:PE0)
Port E is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port E
output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs,
Port E pins that are externally pulled low will source current if the pull-up resistors are activated. The Port
E pins are tristated when a reset condition becomes active, even if the clock is not running.
Port E also serves the functions of various special features of the ATmega64A as listed in Alternate
Functions of Port E.
6.1.8. Port F (PF7:PF0)
Port F serves as the analog inputs to the A/D Converter.
Atmel ATmega64A [DATASHEET]
Atmel-8160ES-8-bit AVR Micrcontroller_Datasheet_Summary-09/2015
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