Datasheet

28
ATmega8A [DATASHEET]
8159E–AVR–02/2013
Figure 9-3. External RC Configuration
The Oscillator can operate in four different modes, each optimized for a specific frequency range. The operating
mode is selected by the fuses CKSEL3:0 as shown in Table 9-6.
When this Oscillator is selected, start-up times are determined by the SUT Fuses as shown in Table 9-7.
Note: 1. This option should not be used when operating close to the maximum frequency of the device.
Table 9-6. External RC Oscillator Operating Modes
CKSEL3:0 Frequency Range (MHz)
0101 0.1 - 0.9
0110 0.9 - 3.0
0111 3.0 - 8.0
1000 8.0 - 12.0
Table 9-7. Start-up Times for the External RC Oscillator Clock Selection
SUT1:0
Start-up Time from
Power-down and
Power-save
Additional Delay
from Reset
(V
CC
= 5.0V) Recommended Usage
00 18 CK – BOD enabled
01 18 CK 4.1 ms Fast rising power
10 18 CK 65 ms Slowly rising power
11 6 CK
(1)
4.1 ms Fast rising power or BOD enabled
XTAL2
XTAL1
GND
C
R
V
CC
NC