Atmel ATmega128 Manual page 7

RESET
XTAL1
XTAL2
AVCC
AREF
PEN
2467S–AVR–07/09
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
51. Shorter pulses are not guaranteed to generate a reset.
Input to the inverting Oscillator amplifier and input to the internal clock operating circuit.
Output from the inverting Oscillator amplifier.
AVCC is the supply voltage pin for Port F and the A/D Converter. It should be externally con-
nected to V , 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 is the analog reference pin for the A/D Converter.
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.
ATmega128
Table 19 on page
CC
7