Rainbow-electronics ATmega64L Bedienungsanleitung PDF herunterladen (Seite 25)

ATmega16(L)

2466B–09/01

The CKSEL0 fuse together with the SUT1..0 fuses select the start-up times as shown in

Table 5.

Notes: 1. These options should only be used when not operating close to the maximum fre-

quency of the device, and only if frequency stability at start-up is not important for the

application. These options are not suitable for crystals.

2. These options are intended for use with ceramic resonators and will ensure fre-

quency stability at start-up. They can also be used with crystals when not operating

close to the maximum frequency of the device, and if frequency stability at start-up is

not important for the application.

Low-frequency Crystal

Oscillator

To use a 32.768 kHz watch crystal as the clock source for the device, the low-frequency

crystal oscillator must be selected by setting the CKSEL fuses to “1001”. The crystal

should be connected as shown in Figure 12. By programming the CKOPT fuse, the user

can enable internal capacitors on XTAL1 and XTAL2, thereby removing the need for

external capacitors. The internal capacitors have a nominal value of 36 pF. Refer to the

32 kHz Crystal Oscillator application note for details on oscillator operation and how to

choose appropriate values for C1 and C2.

Table 5. Start-up Times for the Crystal Oscillator Clock Selection

CKSEL0 SUT1..0

Start-up Time from

Power-down and

Power-save

Additional Delay

from Reset

= 5.0V) Recommended Usage

000 258 CK

(1)

4 ms

Ceramic resonator, fast

rising power

001 258 CK

(1)

64 ms

Ceramic resonator, slowly

rising power

010 1K CK

(2)

–

Ceramic resonator, BOD

enabled

011 1K CK

(2)

4 ms

Ceramic resonator, fast

rising power

100 1K CK

(2)

64 ms

Ceramic resonator, slowly

rising power

1 01 16K CK –

Crystal oscillator, BOD

enabled

1 10 16K CK 4 ms

Crystal oscillator, fast

rising power

1 11 16K CK 64 ms

Crystal oscillator, slowly

rising power

1 2 ... 20 21 22 23 24 25 26 27 28 29 30 ... 297 298

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