ATMEGA329 データシートの表示（PDF） - Atmel Corporation

部品番号

コンポーネント説明

メーカー

ATMEGA329

8-bit Microcontroller with In-System Programmable Flash

Atmel Corporation 

9.3 Crystal Oscillator

XTAL1 and XTAL2 are input and output, respectively, of an inverting amplifier which can be con-

figured for use as an On-chip Oscillator, as shown in Figure 9-2. Either a quartz crystal or a

ceramic resonator may be used.

C1 and C2 should always be equal for both crystals and resonators. The optimal value of the

capacitors depends on the crystal or resonator in use, the amount of stray capacitance, and the

electromagnetic noise of the environment. Some initial guidelines for choosing capacitors for

use with crystals are given in Table 9-3. For ceramic resonators, the capacitor values given by

the manufacturer should be used.

Figure 9-2. Crystal Oscillator Connections

C2

XTAL2

C1

XTAL1

GND

The Oscillator can operate in three different modes, each optimized for a specific frequency

range. The operating mode is selected by the fuses CKSEL3..1 as shown in Table 9-3.

Table 9-3. Crystal Oscillator Operating Modes

CKSEL3..1

100(1)

Frequency Range

(MHz)

0.4 - 0.9

Recommended Range for Capacitors C1

and C2 for Use with Crystals (pF)

–

101

0.9 - 3.0

12 - 22

110

3.0 - 8.0

12 - 22

111

8.0 -

12 - 22

Notes: 1. This option should not be used with crystals, only with ceramic resonators.

The CKSEL0 Fuse together with the SUT1..0 Fuses select the start-up times as shown in Table

9-4.

Table 9-4. Start-up Times for the Crystal Oscillator Clock Selection

CKSEL0 SUT1..0

0

00

Start-up Time from

Power-down and

Power-save

258 CK(1)

0

01

258 CK(1)

0

10

1K CK(2)

Additional Delay

from Reset

(VCC = 5.0V)

14CK + 4.1 ms

14CK + 65 ms

14CK

Recommended

Usage

Ceramic resonator,

fast rising power

Ceramic resonator,

slowly rising power

Ceramic resonator,

BOD enabled

28 ATmega329/3290/649/6490

2552J–AVR–08/07

Share Link: