ATtiny167-ESMZ datasheet(29/282 Pages) ATMEL

29 / 282 page

7728D–AVR–07/09

ATtiny87/ATtiny167

The CKSEL0 Fuse together with the SUT1..0 Fuses or CSEL0 together with CSUT1..0 field

select the start-up times as shown in Table 4-7.

Notes:

1. Flash Fuse bits.

2. CLKSELR register bits.

3. These options should only be used when not operating close to the maximum frequency of

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

These options are not suitable for crystals.

4. These options are intended for use with ceramic resonators and will ensure frequency stabil-

ity 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.

5. This setting is only available if RSTDISBL fuse is not set.

4.2.5

Low-frequency Crystal Oscillator

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

tal oscillator must be selected by setting CKSEL fuses or CSEL field as shown in Table 4-1 on

page 25. The crystal should be connected as shown in Figure 4-3. Refer to the 32.768 kHz

Crystal Oscillator Application Note for details on oscillator operation and how to choose appro-

priate values for C1 and C2.

The 32.768 kHz watch crystal oscillator can be used by the asynchronous timer if the

(high-frequency) Crystal Oscillator is not running or if the External Clock is not enabed (See

”Enable/Disable Clock Source” on page 32.). The asynchronous timer is then able to start

itself this low-frequency crystal oscillator.

Table 4-7.

Start-up Times for the Crystal Oscillator Clock Selection

CKSEL0(1)

CSEL0(2)

SUT1..0(1)

CSUT1..0(2)

Start-up Time from

Power-down/save

Additional Delay

from Reset

(Vcc = 5.0V)

Recommended Usage

258 CK(3)

14CK + 4.1 ms

Ceramic resonator, fast

rising power

258 CK(3)

14CK + 65 ms

Ceramic resonator, slowly

rising power

010(5)

1K (1024) CK(4)

14CK

Ceramic resonator, BOD

enabled

1K (1024)CK(4)

14CK + 4.1 ms

Ceramic resonator, fast

rising power

1K (1024)CK(4)

14CK + 65 ms

Ceramic resonator, slowly

rising power

101(5)

16K (16384) CK

14CK

Crystal Oscillator, BOD

enabled

16K (16384) CK

14CK + 4.1 ms

Crystal Oscillator, fast

rising power

16K (16384) CK

14CK + 65 ms

Crystal Oscillator, slowly

rising power

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