31
8008H–AVR–04/11
ATtiny48/88
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-
When this oscillator is selected, start-up times are determined by the SUT Fuses as shown in
the table below.
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.
2.
The device is shipped with this option selected.
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 patch variations. This clock may be
selected as the system clock by programming the CKSEL Fuses to “11”.
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.
6.2.4
Default Clock Source
The device is shipped with internal oscillator at 8.0 MHz and with the fuse CKDIV8 programmed,
resulting in 1.0 MHz system clock. The startup time is set to maximum and time-out period
enabled (CKSEL = 0b10, SUT = 0b10, CKDIV8 = 0). The default setting ensures that all users
can make their desired clock source setting using any available programming interface.
6.3
System Clock Prescaler
The ATtiny48/88 has a system clock prescaler, and the system clock can be divided by setting
system clock frequency and the power consumption when the requirement for processing power
Table 6-3.
Start-up Times for the Internal Calibrated Oscillator Clock Selection
SUT[1:0]
Power Conditions
Start-up Time
from Power-down
Additional Delay
from Reset (VCC = 5.0V)
00
BOD enabled
6 CK
01
Fast rising power
6 CK
14CK + 4 ms
Slowly rising power
6 CK
14CK + 64 ms
11
Reserved
Table 6-4.
Start-up Times for the 128 kHz Internal Oscillator
SUT[1:0]
Power Conditions
Start-up Time
from Power-down
Additional Delay
from Reset
00
BOD enabled
6 CK
01
Fast rising power
6 CK
14CK + 4 ms
10
Slowly rising power
6 CK
14CK + 64 ms
11
Reserved