Atmel ATmega328P Xplained Mini MEGA328P-XMINI MEGA328P-XMINI Data Sheet
Product codes
MEGA328P-XMINI
34
ATmega48A/PA/88A/PA/168A/PA/328/P [DATASHEET]
Atmel-8271H-AVR- ATmega-Datasheet_08/2014
Note:
1.
This option should only be used if frequency stability at start-up is not important for the application
9.6
Calibrated Internal RC Oscillator
By default, the Internal RC Oscillator provides an approximate 8.0MHz clock. Though voltage and temperature
dependent, this clock can be very accurately calibrated by the user. See
dependent, this clock can be very accurately calibrated by the user. See
for more
details. The device is shipped with the CKDIV8 Fuse programmed. See
for more details.
. If
selected, it will operate with no external components. During reset, hardware loads the pre-programmed
calibration value into the OSCCAL Register and thereby automatically calibrates the RC Oscillator. The
accuracy of this calibration is shown as Factory calibration in
calibration value into the OSCCAL Register and thereby automatically calibrates the RC Oscillator. The
accuracy of this calibration is shown as Factory calibration in
By changing the OSCCAL register from SW, see
, it is
possible to get a higher calibration accuracy than by using the factory calibration. The accuracy of this
calibration is shown as User calibration in
calibration is shown as User calibration in
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 calibration value, see the section
and for the Reset Time-out. For more information on the pre-programmed calibration value, see the section
.
Notes: 1.
The device is shipped with this option selected.
2.
If 8MHz frequency exceeds the specification of the device (depends on V
CC
), the CKDIV8 Fuse can be
programmed in order to divide the internal frequency by 8.
When this Oscillator is selected, start-up times are determined by the SUT Fuses as shown in
Note:
1.
If the RSTDISBL fuse is programmed, this start-up time will be increased to
14CK + 4.1ms to ensure programming mode can be entered.
14CK + 4.1ms to ensure programming mode can be entered.
2.
The device is shipped with this option selected.
Table 9-10.
Start-up Times for the Low-frequency Crystal Oscillator Clock Selection
CKSEL3...
0
Start-up Time from
Power-down and Power-save
Recommended Usage
0100
1K CK
0101
32K CK
Stable frequency at start-up
Table 9-11.
Internal Calibrated RC Oscillator Operating Modes
Frequency Range
CKSEL3...0
7.3 - 8.1
0010
Table 9-12.
Start-up times for the internal calibrated RC Oscillator clock selection
Power Conditions
Start-up Time from Power-
down and Power-save
Additional Delay from
Reset (V
CC
= 5.0V)
SUT1...0
BOD enabled
6 CK
14CK
00
Fast rising power
6 CK
14CK + 4.1ms
01
Slowly rising power
6 CK
14CK + 65ms
10
Reserved
11