ATEMGA128L View Datasheet(PDF) - Atmel Corporation
Part Name
Description
MFG CO.
'ATEMGA128L' PDF : 395 Pages View PDF
ATmega128
Low-frequency Crystal
Oscillator
Table 9. Start-up Times for the Crystal Oscillator Clock Selection
CKSEL0
0
SUT1..0
00
0
01
0
10
0
11
1
00
Start-up Time from
Power-down and
Power-save
258 CK(1)
258 CK(1)
1K CK(2)
1K CK(2)
1K CK(2)
Additional Delay
from Reset (VCC
= 5.0V)
4.1 ms
65 ms
–
4.1 ms
65 ms
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
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
Notes:
1. These options should only be used when not operating close to the maximum fre-
quency 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 fre-
quency stability at start-up. They can also be used with crystals when not operating
close to the maximum frequency of the device, and if frequency stability at start-up is
not important for the application.
To use a 32.768 kHz watch crystal as the clock source for the device, the Low-fre-
quency Crystal Oscillator must be selected by setting the CKSEL fuses to “1001”. The
crystal should be connected as shown in Figure 19. By programming the CKOPT fuse,
the user can enable internal capacitors on XTAL1 and XTAL2, thereby removing the
need for external capacitors. The internal 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 10.
Table 10. Start-up Times for the Low-frequency Crystal Oscillator Clock Selection
SUT1..0
Start-up Time from
Power-down and
Power-save
Additional Delay
from Reset (VCC =
5.0V)
Recommended Usage
00
1K CK(1)
4.1 ms
Fast rising power or BOD enabled
01
1K CK(1)
65 ms
Slowly rising power
10
32K CK
65 ms
Stable frequency at start-up
11
Reserved
Note: 1. These options should only be used if frequency stability at start-up is not important
for the application.
39
2467O–AVR–10/06
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