ata5773 ATMEL Corporation, ata5773 Datasheet - Page 77

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

6.2.2
8006G–AVR–01/08
Calibrated Internal 8 MHz Oscillator
Figure 6-2.
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table
Table 6-3.
When applying an external clock, it is required to avoid sudden changes in the applied clock fre-
quency to ensure stable operation of the MCU. A variation in frequency of more than 2% from
one clock cycle to the next can lead to unpredictable behavior. It is required to ensure that the
MCU is kept in Reset during such changes in the clock frequency.
Note that the System Clock Prescaler can be used to implement run-time changes of the internal
clock frequency while still ensuring stable operation. See
for details.
By default, the Internal RC Oscillator provides an approximate 8 MHz clock. Though voltage and
temperature dependent, this clock can be very accurately calibrated by the user. See
on page 178
with the CKDIV8 Fuse programmed. See
This clock may be selected as the system clock by programming the CKSEL Fuses as shown in
Table
the pre-programmed calibration value into the OSCCAL Register and thereby automatically cal-
ibrates the RC Oscillator. The accuracy of this calibration is shown as Factory calibration in
Table 20-2 on page
By changing the OSCCAL register from SW, see
page
The accuracy of this calibration is shown as User calibration in
SUT1..0
00
01
10
11
29, it is possible to get a higher calibration accuracy than by using the factory calibration.
6-3.
6-4. If selected, it will operate with no external components. During reset, hardware loads
and
External Clock Drive Configuration
Start-up Times for the External Clock Selection
EXTERNAL
“Internal Oscillator Speed” on page 206
from Power-down
178.
SIGNAL
Start-up Time
CLOCK
6 CK
6 CK
6 CK
“System Clock Prescaler” on page 29
Additional Delay
Reserved
“OSCCAL – Oscillator Calibration Register” on
14CK + 64 ms
14CK + 4 ms
from Reset
14CK
CLKI
GND
for more details. The device is shipped
“System Clock Prescaler” on page 29
Table 20-2 on page
ATtiny24/44/84
BOD enabled
Fast rising power
Slowly rising power
Recommended
for more details.
Usage
178.
Table 20-2
25