ATmega64A datasheet(7/392 Pages) ATMEL

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8160C–AVR–07/09

ATmega64A

2.3.9

Port G (PG4:PG0)

Port G is a 5-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The

Port G output buffers have symmetrical drive characteristics with both high sink and source

capability. As inputs, Port G pins that are externally pulled low will source current if the pull-up

resistors are activated. The Port G pins are tri-stated when a reset condition becomes active,

even if the clock is not running.

Port G also serves the functions of various special features.

In ATmega103 compatibility mode, these pins only serves as strobes signals to the external

memory as well as input to the 32 kHz 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.

2.3.10

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 28-3 on page

330. Shorter pulses are not guaranteed to generate a reset.

2.3.11

XTAL1

Input to the inverting Oscillator amplifier and input to the internal clock operating circuit.

2.3.12

XTAL2

Output from the inverting Oscillator amplifier.

2.3.13

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 VCC

through a low-pass filter.

2.3.14

AREF

AREF is the analog reference pin for the A/D Converter.

2.3.15

PEN

This is a programming enable pin for the SPI Serial Programming mode. By holding this pin low

during a Power-on Reset, the device will enter the SPI Serial Programming mode. PEN is inter-

nally pulled high. The pullup is shown in Figure 10-1 on page 52 and its value is given in Section

28.2 “DC Characteristics” on page 327. PEN has no function during normal operation.

Resources

A comprehensive set of development tools, application notes and datasheetsare available for

download on http://www.atmel.com/avr.

Note:

Data Retention

Reliability Qualification results show that the projected data retention failure rate is much less

than 1 PPM over 20 years at 85°C or 100 years at 25°C.

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