5
ATmega64A [DATASHEET]
8160D–AVR–02/2013
Boot Loader capabilities is not supported.
It is not possible to adjust the frequency of the internal calibrated RC Oscillator.
The External Memory Interface can not release any Address pins for general I/O, neither configure different wait
states to different External Memory Address sections.
Only EXTRF and PORF exist in the MCUCSR Register.
No timed sequence is required for Watchdog Timeout change.
Only low-level external interrupts can be used on four of the eight External Interrupt sources.
Port C is output only.
USART has no FIFO buffer, so Data OverRun comes earlier.
The user must have set unused I/O bits to 0 in ATmega103 programs.
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 is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port A output buf-
fers 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 ATmega64A as listed on
page 72.2.3.4
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 buf-
fers 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 ATmega64A as listed on
page 73.2.3.5
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 buf-
fers 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 tri-stated 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 on
page 76. In ATmega103 com-
patibility mode, Port C is output only, and the port C pins are not tri-stated when a reset condition becomes active.
2.3.6
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 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.
Port D also serves the functions of various special features of the ATmega64A as listed on
page 77.