7
8152GS–AVR–11/09
ATmega164PA/324PA/644PA/1284P
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.
P o r t A a l s o s e r v e s t h e f u n c t i o n s o f v a r i o u s s p e c i a l f e a t u r e s o f t h e
ATmega164PA/324PA/644PA/1284P as listed on
page 81
.
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.
P o r t B a l s o s e r v e s t h e f u n c t i o n s o f v a r i o u s s p e c i a l f e a t u r e s o f t h e
ATmega164PA/324PA/644PA/1284P as listed on
page 83
.
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
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 the JTAG interface, along with special features of the
ATmega164PA/324PA/644PA/1284P as listed on
page 86
.
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 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 tri-stated when a reset condition becomes active,
even if the clock is not running.
P o r t D a l s o s e r v e s t h e f u n c t i o n s o f v a r i o u s s p e c i a l f e a t u r e s o f t h e
ATmega164PA/324PA/644PA/1284P as listed on
page 88
.
