ATtiny48 datasheet(29/266 Pages) ATMEL

29 / 266 page

8008C–AVR–03/09

ATtiny48/88

When this clock source is selected, start-up times are determined by the SUT Fuses as shown in

Table 6-6.

Note:

1. If the RSTDISBL fuse is programmed, this start-up time will be increased to 14CK + 4 ms to

ensure programming mode can be entered.

6.5

External Clock

To drive the device from an external clock source, CLKI should be driven as shown in Figure 6-2

on page 29. To run the device on an external clock, the CKSEL Fuses must be programmed to

“00” (see Table 6-7).

Figure 6-2.

External Clock Drive Configuration

When this clock source is selected, start-up times are determined by the SUT Fuses as shown in

Table 6-8.

Table 6-6.

Start-up Times for the 128 kHz Internal Oscillator

SUT1..0

Power Conditions

Start-up Time

from Power-down

Additional Delay

from Reset

BOD enabled

6 CK

14CK(1)

Fast rising power

6 CK

14CK + 4 ms

Slowly rising power

6 CK

14CK + 64 ms

Reserved

Table 6-7.

Selecting External Clock

CKSEL1..0

Frequency

– 12 MHz

Table 6-8.

Start-up Times for the External Clock Selection

SUT1..0

Power Conditions

Start-up Time

from Power-down

Additional Delay

from Reset (V

CC = 5.0V)

BOD enabled

6 CK

14CK

EXTERNAL

CLOCK

SIGNAL

CLKI

GND

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