ATMEGA103(1999) View Datasheet(PDF) - Atmel Corporation

Part Name

Description

Manufacturer

ATMEGA103
(Rev.:1999)

8-bit Microcontroller with 64K/128K Bytes In-System Programmable Flash

Atmel Corporation 

Clock Options

Crystal Oscillator

XTAL1 and XTAL2 are input and output, respectively, of an inverting amplifier which can be configured for use as an on-

chip oscillator, as shown in Figure 2. Either a quartz crystal or a ceramic resonator may be used.

Figure 2. Oscillator Connections

MAX 1 HC BUFFER

HC

C2

XTAL2

C1

XTAL1

GND

Note: When using the MCU Oscillator as a clock for an external device, an HC buffer should be connected as indicated in the figure.

External Clock

To drive the device from an external clock source, XTAL2 should be left unconnected while XTAL1 is driven as shown in

Figure 3.

Figure 3. External Clock Drive Configuration

NC

EXTERNAL

OSCILLATOR

SIGNAL

XTAL2

XTAL1

GND

Timer Oscillator

For the Timer Oscillator pins, TOSC1 and TOSC2, the crystal is connected directly between the pins. No external capaci-

tors are needed. The oscillator is optimized for use with a 32,768 Hz watch crystal. An external clock signal applied to this

pin goes through the same amplifier having a bandwidth of 256 kHz. The external clock signal should therefore be in the

range 0 Hz - 256 kHz.

6

ATmega603/103

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