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ATtiny25/45/85 [DATASHEET]
2586Q–AVR–08/2013
When the calibrated 8 MHz internal oscillator is selected as clock source the start-up times are determined by the
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.
In ATtiny15 Compatibility Mode start-up times are determined by SUT fuses as shown in
Table 6-8 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.
In summary, more information on ATtiny15 Compatibility Mode can be found in sections
“Port B (PB5:PB0)” on6.2.4
Internal 128 kHz Oscillator
The 128 kHz internal Oscillator is a low power Oscillator providing a clock of 128 kHz. The frequency is nominal at
3V and 25
C. This clock may be select 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
Table 6-9.
Table 6-7.
Start-up Times for Internal Calibrated RC Oscillator Clock
SUT[1:0]
Start-up Time
from Power-down
Additional Delay from
Reset (V
CC = 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 6-8.
Start-up Times for Internal Calibrated RC Oscillator Clock (in ATtiny15 Mode)
SUT[1:0]
Start-up Time
from Power-down
Additional Delay from
Reset (VCC = 5.0V)
Recommended Usage
00
6 CK
14CK + 64 ms
01
6 CK
14CK + 64 ms
10
6 CK
14CK + 4 ms
11
1 CK
Table 6-9.
Start-up Times for the 128 kHz Internal Oscillator
SUT[1:0]
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