AT90PWM216-16SE ATMEL [ATMEL Corporation], AT90PWM216-16SE Datasheet - Page 32

• Manufacturer Part Number: AT90PWM216-16SE
• Description: 8-bit Microcontroller with 16K Bytes In-System Programmable flash
• Manufacturer: ATMEL [ATMEL Corporation]

7.5
32
Calibrated Internal RC Oscillator
AT90PWM216/316
Table 7-4.
Notes:
By default, the Internal RC OScillator provides an approximate 8.0 MHz clock. Though voltage
and temperature dependent, this clock can be very accurately calibrated by the user. The device
is shipped with the CKDIV8 Fuse programmed. See
more details.
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 26-1 on page
By changing the OSCCAL register from SW, see
page
The accuracy of this calibration is shown as User calibration in
page
When this Oscillator is used as the chip clock, the Watchdog Oscillator will still be used for the
Watchdog Timer and for the Reset Time-out. For more information on the pre-programmed cali-
bration value, see the section
CKSEL0
0
0
0
0
1
1
1
1
285.
33, it is possible to get a higher calibration accuracy than by using the factory calibration.
7-5. If selected, it will operate with no external components. During reset, hardware loads
1. These options should only be used when not operating close to the maximum frequency of the
2. These options are intended for use with ceramic resonators and will ensure frequency stability
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.
SUT1..0
Start-up Times for the Oscillator Clock Selection
00
01
10
11
00
01
10
11
304.
Start-up Time from
Power-down and
Power-save
Section “Calibration Byte”, page
258 CK
258 CK
1K CK
1K CK
1K CK
16K CK
16K CK
16K CK
(2)
(2)
(2)
(1)
(1)
“Oscillator Calibration Register – OSCCAL” on
Additional Delay
14CK + 4.1 ms
14CK + 4.1 ms
14CK + 4.1 ms
14CK + 65 ms
14CK + 65 ms
14CK + 65 ms
(V
from Reset
“System Clock Prescaler” on page 37
CC
14CK
14CK
= 5.0V)
285.
Section “Calibration Byte”,
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
7710D–AVR–08/09
for