ata5773 ATMEL Corporation, ata5773 Datasheet - Page 79

• Manufacturer Part Number: ata5773
• Description: Microcontroller With Uhf Ask/fsk Transmitter
• Manufacturer: ATMEL Corporation

6.2.4
6.2.5
8006G–AVR–01/08
Low-Frequency Crystal Oscillator
Crystal Oscillator / Ceramic Resonator
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 CKSEL fuses to ‘0110’. The crystal should be connected
as shown in
For this oscillator start-up times can be set with the SUT fuses, as shown in
Table 6-7.
Notes:
XTAL1 and XTAL2 are input and output, respectively, of an inverting amplifier which can be con-
figured for use as an On-chip Oscillator, as shown in
ceramic resonator may be used.
Figure 6-3.
C1 and C2 should always be equal for both crystals and resonators. The optimal value of the
capacitors depends on the crystal or resonator in use, the amount of stray capacitance, and the
electromagnetic noise of the environment. Some initial guidelines for choosing capacitors for
use with crystals are given in
given by the manufacturer should be used.
Table 6-8.
Notes:
SUT1..0
CKSEL3..1
00
01
10
11
100
101
110
111
(1)
1. These options should be used only if frequency stability at start-up is not important
1. This option should not be used with crystals, only with ceramic resonators.
Figure
Start-up Times for the Low Frequency Crystal Oscillator Clock Selection
Crystal Oscillator Connections
Crystal Oscillator Operating Modes
from Power Down
Start-up Time
6-3. To find suitable capacitors please consult the manufacturer’s datasheet.
1K CK
1K CK
32K CK
Frequency Range (MHz)
(1)
(1)
0.4 - 0.9
0.9 - 3.0
3.0 - 8.0
8.0 -
Table 6-8
C2
C1
Additional Delay
below. For ceramic resonators, the capacitor values
from Reset
64 ms
64 ms
4 ms
Reserved
Recommended C1 and C2 Value (pF)
XTAL2
XTAL1
GND
Figure 6-3
Recommended usage
Fast rising power or BOD enabled
Slowly rising power
Stable frequency at start-up
ATtiny24/44/84
Either a quartz crystal or a
12 - 22
12 - 22
12 - 22
–
Table
6-7.
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