Rainbow-electronics Atmega169L Manuel d'utilisateur télécharger pdf (Page 26)

ATmega169V/L

2514A–AVR–08/02

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 “0100”, “0101”,

“0110”,or“0111”. The crystal should be connected as shown in Figure 12. When this

Oscillator is selected, start-up times are determined by the SUT Fuses as shown in

Table 6 and CKSEL1..0 as shown in Table 7.

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 258CK

(1)

14CK + 4.1 ms Ceramic resonator, fast

rising power

001 258CK

(1)

14CK + 65 ms Ceramic resonator,

slowly rising power

010 1KCK

(2)

14CK Ceramic resonator,

BOD enabled

011 1KCK

(2)

14CK + 4.1 ms Ceramic resonator, fast

rising power

100 1KCK

(2)

14CK + 65 ms Ceramic resonator,

slowly rising power

01 16K CK 14CK Crystal Oscillator, BOD

enabled

10 16K CK 14CK + 4.1 ms Crystal Oscillator, fast

rising power

11 16K CK 14CK + 65 ms Crystal Oscillator,

slowly rising power

Table 6. Start-up Times for the Low-frequency Crystal Oscillator Clock Selection

SUT1..0 Additional Delay from Reset (V

= 5.0V) Recommended Usage

00 14CK Fast rising power or BOD enabled

01 14CK + 4.1 ms Slowly rising power

10 14CK + 65 ms Stable frequency at start-up

11 Reserved

1 2 ... 21 22 23 24 25 26 27 28 29 30 31 ... 316 317

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Rainbow-electronics Atmega169L Manuel d'utilisateur Page 26

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