ATmega128
In ATmega103 compatibility mode, these pins only serves as strobes signals to the external
memory as well as input to the 32kHz Oscillator, and the pins are initialized to PG0 = 1, PG1 = 1,
and PG2 = 0 asynchronously when a reset condition becomes active, even if the clock is not
running. PG3 and PG4 are oscillator pins.
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 19 on page
50.
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
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 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.
XTAL1
XTAL2
AVCC
AREF
PEN
7
2467XS–AVR–06/11
ATMEL [ ATMEL CORPORATION ]
