ATMEGA8-16AI SL383 Atmel, ATMEGA8-16AI SL383 Datasheet - Page 28

• Manufacturer Part Number: ATMEGA8-16AI SL383
• Description: Semiconductors and Actives, Microprocessors, Microcontrollers
• Manufacturer: Atmel

Low-frequency
Crystal Oscillator
External RC
Oscillator
28
ATmega8(L)
Table 5. Start-up Times for the Crystal Oscillator Clock Selection
Notes:
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
CKSEL0
SUT1..0
00
01
10
11
0
0
0
0
1
1
1
1
6.
1. These options should only be used when not operating close to the maximum frequency of the
2. These options are intended for use with ceramic resonators and will ensure frequency stability
1. These options should only be used if frequency stability at start-up is not important for the
device, and only if frequency stability at start-up is not important for the application. These
options are not suitable for crystals.
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.
application.
SUT1..0
Start-up Time from
Power-down and
00
01
10
11
00
01
10
11
Power-save
1K CK
1K CK
32K CK
Figure
from Power-down
and Power-save
(1)
(1)
Start-up Time
258 CK
258 CK
1K CK
1K CK
1K CK
11. By programming the CKOPT Fuse, the user can enable internal
16K CK
16K CK
16K CK
(2)
(2)
(2)
(1)
(1)
Additional Delay
(V
from Reset
CC
4.1 ms
65 ms
65 ms
= 5.0V)
Additional Delay
Reserved
(V
from Reset
CC
4.1 ms
4.1 ms
4.1 ms
65 ms
65 ms
65 ms
= 5.0V)
–
–
Recommended Usage
Fast rising power or BOD enabled
Slowly rising power
Stable frequency at start-up
Recommended Usage
Ceramic resonator, fast
rising power
Ceramic resonator, slowly
rising power
Ceramic resonator, BOD
enabled
Ceramic resonator, fast
rising power
Ceramic resonator, slowly
rising power
Crystal Oscillator, BOD
enabled
Crystal Oscillator, fast
rising power
Crystal Oscillator, slowly
rising power
Figure 12
2486W–AVR–02/10
can be