Rainbow Electronics ATmega8515L - Manual (Page 33)

33
ATmega8515(L)
2512A–AVR–04/02
Figure 18. Crystal Oscillator Connections
The Oscillator can operate in three different modes, each optimized for a specific fre-
quency range. The operating mode is selected by the fuses CKSEL3..1 as shown in
Table 7.
Notes: 1. The frequency ranges are preliminary values. Actual values are TBD.
2. This option should not be used with crystals, only with ceramic resonators.
The CKSEL0 Fuse together with the SUT1..0 fuses select the start-up times as shown in
Table 8.
Table 7. Crystal Oscillator Operating Modes
CKOPT CKSEL3..1
Frequency Range (1)
(MHz)
Recommended Range for Capacitors
C1 and C2 for Use with Crystals (pF)
1 101 (2) 0.4 - 0.9 –
1 110 0.9 - 3.0 12 - 22
1 111 3.0 - 8.0 12 - 22
0 101, 110, 111 1.0 - 12 - 22
Table 8. Start-up Times for the Crystal Oscillator Clock Selection
CKSEL0 SUT1..0
Start-up Time
from Power-down
Additional Delay from
Reset (V
CC
= 5.0V)
Recommended
Usage
0 00 258 CK (1) 4.1 ms Ceramic resonator,
fast rising power
0 01 258 CK (1) 65 ms Ceramic resonator,
slowly rising power
0 10 1K CK (2) – Ceramic resonator,
BOD enabled
0 11 1K CK (2) 4.1 ms Ceramic resonator,
fast rising power
1 00 1K CK (2) 65 ms Ceramic resonator,
slowly rising power
1 01 16K CK – Crystal oscillator,
BOD enabled
1 10 16K CK 4.1 ms Crystal oscillator, fast
rising power
1 11 16K CK 65 ms Crystal oscillator,
slowly rising power
XTAL2
XTAL1
GND
C2
C1