Datasheet

27
7728G–AVR–06/10
ATtiny87/ATtiny167
Notes: 1. If 8 MHz frequency exceeds the specification of the device (depends on Vcc), the CKDIV8
fuse can be programmed in order to divide the internal frequency by 8.
2. The frequency ranges are guideline values.
3. The device is shipped with this CKSEL = “0010”.
4. Flash Fuse bits.
5. CLKSELR register bits.
When this Oscillator is selected, start-up times are determined by the SUT Fuses or by CSUT
field as shown in Table 4-4.
Notes: 1. Flash Fuse bits
2. CLKSELR register bits
3. This setting is only available if RSTDISBL fuse is not set
4. The device is shipped with this option selected.
4.2.3 128 KHz Internal 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 selected as the system clock by pro-
gramming CKSEL Fuses or CSEL field as shown in Table 4-1 on page 25.
When this clock source is selected, start-up times are determined by the SUT Fuses or by
CSUT field as shown in Table 4-5.
Notes: 1. Flash Fuse bits
2. CLKSELR register bits
3. This setting is only available if RSTDISBL fuse is not set
Table 4-3. Internal Calibrated RC Oscillator Operating Modes
(1)
Frequency Range
(2)
(MHz)
CKSEL3..0
(3)(4)
CSEL3..0
(5)
7.6 - 8.4 0010
Table 4-4. Start-up Times for the Internal Calibrated RC Oscillator Clock Selection
SUT1..0
(1)
CSUT1..0
(2)
Start-up Time from
Power-down/save
Additional Delay from
Reset (Vcc = 5.0V) Recommended Usage
00
(3)
6 CK 14CK BOD enabled
01 6 CK 14CK + 4.1 ms Fast rising power
10
(4)
6 CK 14CK + 65 ms Slowly rising power
11 Reserved
Table 4-5. Start-up Times for the 128 kHz Internal Oscillator
SUT1..0
(1)
CSUT1..0
(2)
Start-up Time from
Power-down/save
Additional Delay
from Reset
(Vcc = 5.0V) Recommended Usage
00
(3)
6 CK 14CK BOD enabled
01 6 CK 14CK + 4.1 ms Fast rising power
10 6 CK 14CK + 65 ms Slowly rising power
11 Reserved