ATMEGA8A_14 Datasheet, PDF (5/320 Pages) ATMEL Corporation – 8-bit Atmel Microcontroller with 8KB In-System Programmable Flash

The various special features of Port B are elaborated in “Alternate Functions of Port B” on page 56 and “System
Clock and Clock Options” on page 24.
2.2.4
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 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.
2.2.5
PC6/RESET
If the RSTDISBL Fuse is programmed, PC6 is used as an I/O pin. Note that the electrical characteristics of PC6 dif-
fer 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 26-3 on page 228. Shorter pulses are not guaranteed to generate a Reset.
The various special features of Port C are elaborated on page 59.
2.2.6
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 ATmega8A as listed on page 61.
2.2.7
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 26-3 on page 228. Shorter pulses are not guaranteed to
generate a reset.
2.2.8
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.
2.2.9 AREF
AREF is the analog reference pin for the A/D Converter.
2.2.10 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.
ATmega8A [DATASHEET]
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8159E–AVR–02/2013