ATmega8(L)
pF. By programming the CKOPT Fuse, the user can enable an internal 36 pF capacitor between
XTAL1 and GND, thereby removing the need for an external capacitor.
Figure 12. External RC Configuration
V
CC
NC
XTAL2
XTAL1
GND
R
C
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.
Table 7. External RC Oscillator Operating Modes
CKSEL3..0
0101
Frequency Range (MHz)
0.1 - 0.9
0110
0.9 - 3.0
0111
3.0 - 8.0
1000
8.0 - 12.0
When this Oscillator is selected, start-up times are determined by the SUT Fuses as shown in
Table 8.
Table 8. Start-up Times for the External RC Oscillator Clock Selection
Start-up Time from
Power-down and
Power-save
Additional Delay
from Reset
SUT1..0
00
(VCC = 5.0V)
Recommended Usage
BOD enabled
18 CK
18 CK
18 CK
6 CK(1)
–
01
4.1 ms
65 ms
4.1 ms
Fast rising power
10
Slowly rising power
11
Fast rising power or BOD enabled
Note:
1. This option should not be used when operating close to the maximum frequency of the device.
29
2486T–AVR–05/08
ATMEL [ ATMEL ]
