7
2467S–AVR–07/09
ATmega128
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
. Shorter pulses are not guaranteed to generate a reset.
XTAL1
Input to the inverting Oscillator amplifier and input to the internal clock operating circuit.
XTAL2
Output from the inverting Oscillator amplifier.
AVCC
AVCC is the supply voltage pin for Port F and the A/D Converter. It should be externally con-
nected 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.
AREF
AREF is the analog reference pin for the A/D Converter.
PEN
PEN is a programming enable pin for the SPI Serial Programming mode, and is internally pulled
high . By holding this pin low during a Power-on Reset, the device will enter the SPI Serial Pro-
gramming mode. PEN has no function during normal operation.