ATMEga64L ATMEL Corporation, ATMEga64L Datasheet - Page 38

• Manufacturer Part Number: ATMEga64L
• Description: 8-bit AVR Microcontroller with 64K Bytes In-System Programmable Flash
• Manufacturer: ATMEL Corporation

Low-frequency Crystal
Oscillator
38
ATmega64(L)
Table 9. 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-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
Note:
CKSEL0
SUT1..0
00
01
10
11
0
0
0
0
1
1
1
1
1. These options should only be used when not operating close to the maximum fre-
2. These options are intended for use with ceramic resonators and will ensure fre-
1. These options should only be used if frequency stability at start-up is not important
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.
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.
for the application.
SUT1..0
from Power-down
and Power-save
Start-up Time
00
01
10
11
00
01
10
11
1K CK
1K CK
32K CK
Start-up Time from
(1)
(1)
Power-down and
Power-save
258 CK
258 CK
1K CK
1K CK
1K CK
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)
Reserved
Additional Delay
(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
2490G–AVR–03/04