Datasheet

Depending on the clock selection fuse settings, PB6 can be used as input to the inverting Oscillator
amplifier and input to the internal clock operating circuit.
Depending on the clock selection fuse settings, PB7 can be used as output from the inverting Oscillator
amplifier.
If the Internal Calibrated RC Oscillator is used as chip clock source, PB7:6 is used as TOSC2:1 input for
the Asynchronous Timer/Counter2 if the AS2 bit in ASSR is set.
The various special features of Port B are elaborated in Alternate Functions of Port B and System Clock
and Clock Options.
5.1.4 Port C (PC5:PC0)
Port C is an 7-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.
5.1.5 PC6/RESET
If the RSTDISBL Fuse is programmed, PC6 is used as an I/O pin. Note that the electrical characteristics
of PC6 differ from those of the other pins of Port C.
If the RSTDISBL Fuse is unprogrammed, PC6 is used as a Reset input. A low level on this pin for longer
than the minimum pulse length will generate a Reset, even if the clock is not running. The minimum pulse
length is given in Table 30-5. Shorter pulses are not guaranteed to generate a Reset.
The various special features of Port C are elaborated in Alternate Functions of Port C.
5.1.6 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 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 ATmega8A as listed in Alternate
Functions of Port D.
5.1.7 RESET
Reset input. A low level on this pin for longer than the minimum pulse length will generate a reset, even if
the clock is not running. The minimum pulse length is given in Table 30-5. Shorter pulses are not
guaranteed to generate a reset.
5.1.8 AV
CC
AV
CC
is the supply voltage pin for the A/D Converter, Port C (3:0), and ADC (7:6). It should be externally
connected to V
CC
, even if the ADC is not used. If the ADC is used, it should be connected to V
CC
through
a low-pass filter. Note that Port C (5:4) use digital supply voltage, V
CC
.
5.1.9 AREF
AREF is the analog reference pin for the A/D Converter.
5.1.10 ADC7:6 (TQFP and QFN/MLF Package Only)
In the TQFP and QFN/MLF package, ADC7:6 serve as analog inputs to the A/D converter. These pins
are powered from the analog supply and serve as 10-bit ADC channels.
AVR 8-Bit Microcontroller
Pin Configurations
© 2017 Microchip Technology Inc.
Datasheet Complete
40001974A-page 16