ata5773 ATMEL Corporation, ata5773 Datasheet - Page 80

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

6.2.6
28
ATtiny24/44/84
Default Clock Source
The Oscillator can operate in three different modes, each optimized for a specific frequency
range. The operating mode is selected by the fuses CKSEL3..1 as shown in
The CKSEL0 Fuse together with the SUT1..0 Fuses select the start-up times as shown in
6-9 on page
Table 6-9.
Notes:
The device is shipped with CKSEL = “0010”, SUT = “10”, and CKDIV8 programmed. The default
clock source setting is therefore the Internal RC Oscillator running at 8.0 MHz with longest start-
up time and an initial system clock prescaling of 8, resulting in 1.0 MHz system clock. This
default setting ensures that all users can make their desired clock source setting using an in-sys-
tem or high-voltage programmer.
For low-voltage devices (ATtiny24V/44V/84V) it should be noted that unprogramming the
CKDIV8 fuse may result in overclocking. At low voltages (below 2.7V) the devices are rated for
maximum 4 MHz operation (see
internal RC oscillator directly to the system clock line will run the device at 8 MHz.
CKSEL0
0
0
0
0
1
1
1
1
1. When the BOD has been disabled by software, the wake-up time from sleep mode will be
2. These options should only be used when not operating close to the maximum frequency of the
3. These options are intended for use with ceramic resonators and will ensure frequency stability
approximately 60µs to ensure that the BOD is working correctly before the MCU continues
executing code.
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.
28.
SUT1..0
Start-up Times for the Crystal Oscillator Clock Selection
00
01
10
11
00
01
10
11
Start-up Time from
Power-down
258 CK
258 CK
1K CK
1K CK
1K CK
16K CK
16K CK
16K CK
Section 20.3 on page
(3)
(3)
(3)
(2)
(2)
(1)
Additional Delay
14CK + 64 ms
14CK + 64 ms
14CK + 64 ms
14CK + 4 ms
14CK + 4 ms
14CK + 4 ms
from Reset
177), but routing the clock signal from the
14CK
14CK
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
Table
8006G–AVR–01/08
6-8.
Table