ATMEGA16-16AU SL602 Atmel, ATMEGA16-16AU SL602 Datasheet - Page 28

• Manufacturer Part Number: ATMEGA16-16AU SL602
• Manufacturer: Atmel

Low-frequency
Crystal Oscillator
External RC
Oscillator
2466T–AVR–07/10
To use a 32.768 kHz watch crystal as the clock source for the device, the Low-frequency Crystal
Oscillator must be selected by setting the CKSEL Fuses to “1001”. The crystal should be con-
nected as shown in
capacitors on XTAL1 and XTAL2, thereby removing the need for external capacitors. The inter-
nal capacitors have a nominal value of 36 pF.
When this Oscillator is selected, start-up times are determined by the SUT Fuses as shown in
Table
Table 6. Start-up Times for the Low-frequency Crystal Oscillator Clock Selection
Note:
For timing insensitive applications, the external RC configuration shown in
used. The frequency is roughly estimated by the equation f = 1/(3RC). C should be at least 22
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. For more information on
Oscillator operation and details on how to choose R and C, refer to the External RC Oscillator
application note.
Figure 13. 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 7. External RC Oscillator Operating Modes
SUT1..0
00
01
10
11
6.
1. These options should only be used if frequency stability at start-up is not important for the
application.
CKSEL3..0
Start-up Time from
Power-down and
0101
0110
0111
1000
Power-save
1K CK
1K CK
32K CK
Figure
(1)
(1)
12. By programming the CKOPT Fuse, the user can enable internal
R
C
Additional Delay
V
CC
(V
from Reset
CC
4.1 ms
65 ms
65 ms
= 5.0V)
NC
Reserved
Frequency Range (MHz)
Recommended Usage
Fast rising power or BOD enabled
Slowly rising power
Stable frequency at start-up
XTAL2
XTAL1
GND
8.0 - 12.0
0.1 ≤ 0.9
0.9 - 3.0
3.0 - 8.0
ATmega16(L)
Table
Figure 13
7.
can be
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