ATmega88PA Automotive Atmel Corporation, ATmega88PA Automotive Datasheet - Page 33

• Manufacturer Part Number: ATmega88PA Automotive
• Manufacturer: Atmel Corporation

9.6
9223B–AVR–09/11
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
Table 29-3 on page 317
grammed. See
This clock may be selected as the system clock by programming the CKSEL Fuses as shown
in
loads the pre-programmed default 3V calibration value into the OSCCAL Register and thereby
automatically calibrates the RC Oscillator for 3V operation. If the device is to be used at 5V
then the alternate RC Oscillator 5V Calibration Byte
from Signature Row and stored into the OSCCAL register by the user application program for
better 5V frequency accuracy. The accuracy of this calibration is shown as Factory calibration
in
By changing the OSCCAL register from SW, see
on page
tion. The accuracy of this 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
Table 9-11.
When this Oscillator is selected, start-up times are determined by the SUT Fuses as shown in
Table
Table 9-12.
Notes:
Power Conditions
BOD enabled
Fast rising power
Slowly rising power
Note:
Table 29-3 on page
Table
Atmel ATmega48PA/88PA/168PA [Preliminary]
9-12.
1. The device is shipped with this option selected.
2. If 8MHz frequency exceeds the specification of the device (depends on V
1. If the RSTDISBL fuse is programmed, this start-up time will be increased to
2. The device is shipped with this option selected.
37, it is possible to get a higher calibration accuracy than by using the factory calibra-
9-1. If selected, it will operate with no external components. During reset, hardware
Frequency Range
Fuse can be programmed in order to divide the internal frequency by 8.
14CK + 4.1ms to ensure programming mode can be entered.
Internal Calibrated RC Oscillator Operating Modes
Start-up times for the internal calibrated RC Oscillator clock selection
“System Clock Prescaler” on page 36
7.3 - 8.1
317.
for more details. The device is shipped with the CKDIV8 Fuse pro-
Power-down and Power-save
(2)
(MHz)
Start-up Time from
“Calibration Byte” on page
Reserved
6 CK
6 CK
6 CK
“OSCCAL – Oscillator Calibration Register”
for more details.
(Table 27-5 on page
Additional Delay from
298.
Reset (V
14CK + 65ms
14CK + 4.1ms
CKSEL3...0
14CK
0010
Table 29-3 on page
CC
(1)
(1)
= 5.0V)
(2)
286) can be read
CC
), the CKDIV8
SUT1...0
00
01
10
11
317.
33