27
8006K–AVR–10/10
ATtiny24/44/84
ibrates the RC Oscillator. The accuracy of this calibration is shown as Factory calibration in
page 30, it is possible to get a higher calibration accuracy than by using the factory calibration.
When this Oscillator is used as the chip clock, the Watchdog Oscillator will still be used for the
Watchdog Timer and for the Reset Time-out. For more information on the pre-programmed cali-
Note:
1. The device is shipped with this option selected.
When this oscillator is selected, start-up times are determined by the SUT Fuses as shown in
Note:
1. The device is shipped with this option selected.
2. If the RSTDISBL fuse is programmed, this start-up time will be increased to 14CK + 4 ms to
ensure programming mode can be entered.
6.2.3
Internal 128 kHz Oscillator
The 128 kHz internal oscillator is a low power oscillator providing a clock of 128 kHz. The fre-
quency depends on supply voltage, temperature and batch variations. This clock may be
selected as the system clock by programming the CKSEL Fuses to “0100”.
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
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.
Table 6-4.
Internal Calibrated RC Oscillator Operating Modes
CKSEL3:0
Nominal Frequency
0010
8.0 MHz
Table 6-5.
Start-up Times for the Internal Calibrated RC Oscillator Clock Selection
SUT1:0
Start-up Time
from Power-down
Additional Delay from
Reset (VCC = 5.0V)
Recommended Usage
00
6 CK
BOD enabled
01
6 CK
14CK + 4 ms
Fast rising power
6 CK
14CK + 64 ms
Slowly rising power
11
Reserved
Table 6-6.
Start-up Times for the 128 kHz Internal Oscillator
SUT1:0
Start-up Time
from Power-down
Additional Delay
from Reset
Recommended
Usage
00
6 CK
BOD enabled
01
6 CK
14CK + 4 ms
Fast rising power
10
6 CK
14CK + 64 ms
Slowly rising power
11
Reserved