32
8271D–AVR–05/11
ATmega48A/PA/88A/PA/168A/PA/328/P
Figure 9-3.
Crystal Oscillator Connections
Notes:
1. These options should only be used when not operating close to the maximum frequency of the
device, and only if frequency stability at start-up is not important for the application. These
options are not suitable for crystals.
2. These options are intended for use with ceramic resonators and will ensure frequency stability
at start-up. They can also be used with crystals when not operating close to the maximum fre-
quency of the device, and if frequency stability at start-up is not important for the application.
Table 9-6.
Start-up Times for the Full Swing Crystal Oscillator Clock Selection
Oscillator Source /
Power Conditions
Start-up Time from
Power-down and
Power-save
Additional Delay
from Reset
(V
CC
= 5.0V)
CKSEL0
SUT1...0
Ceramic resonator, fast
rising power
258 CK
14CK + 4.1ms
0
00
Ceramic resonator, slowly
rising power
258 CK
14CK + 65ms
0
01
Ceramic resonator, BOD
enabled
1K CK
14CK
0
10
Ceramic resonator, fast
rising power
1K CK
14CK + 4.1ms
0
11
Ceramic resonator, slowly
rising power
1K CK
14CK + 65ms
1
00
Crystal Oscillator, BOD
enabled
16K CK
14CK
1
01
Crystal Oscillator, fast
rising power
16K CK
14CK + 4.1ms
1
10
Crystal Oscillator, slowly
rising power
16K CK
14CK + 65ms
1
11
XTAL2 (TOSC2)
XTAL1 (TOSC1)
GND
C2
C1