ATmega8(L)
least 22pF. By programming the CKOPT Fuse, the user can enable an internal 36pF capacitor
between XTAL1 and GND, thereby removing the need for an external capacitor.
Figure 12.
External RC Configuration
V
CC
NC
R
XTAL2
XTAL1
C
GND
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 7.
External RC Oscillator Operating Modes
CKSEL3..0
0101
0110
0111
1000
Frequency Range (MHz)
0.1 - 0.9
0.9 - 3.0
3.0 - 8.0
8.0 - 12.0
When this Oscillator is selected, start-up times are determined by the SUT Fuses as shown in
Table 8.
Start-up Times for the External RC Oscillator Clock Selection
Start-up Time from
Power-down and
Power-save
18 CK
18 CK
18 CK
6 CK
Additional Delay
from Reset
(V
CC
= 5.0V)
–
4.1ms
65ms
4.1ms
SUT1..0
00
01
10
11
Note:
Recommended Usage
BOD enabled
Fast rising power
Slowly rising power
Fast rising power or BOD enabled
1. This option should not be used when operating close to the maximum frequency of the device
29
2486AA–AVR–02/2013
ATMEL [ ATMEL CORPORATION ]
