AT90PWM2B-16SE ATMEL [ATMEL Corporation], AT90PWM2B-16SE Datasheet - Page 33

• Manufacturer Part Number: AT90PWM2B-16SE
• Description: 8-bit Microcontroller with 8K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

4317J–AVR–08/10
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
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
Table 7-6.
Notes:
When this Oscillator is selected, start-up times are determined by the SUT Fuses as shown in
Table 7-7 on page
Table 7-7.
Note:
Table 7-8.
• Bits 7..0 – CAL7..0: Oscillator Calibration Value
The Oscillator Calibration Register is used to trim the Calibrated Internal RC Oscillator to
remove process variations from the oscillator frequency. The factory-calibrated value is automat-
ically written to this register during chip reset, giving an oscillator frequency of 8.0 MHz at 25°C.
The application software can write this register to change the oscillator frequency. The oscillator
can be calibrated to any frequency in the range 7.3 - 8.1 MHz within ±1% accuracy. Calibration
outside that range is not guaranteed.
Bit
Read/Write
Initial Value
Power Conditions
BOD enabled
Fast rising power
Slowly rising power
33, it is possible to get a higher calibration accuracy than by using the factory calibration.
7-6. If selected, it will operate with no external components. During reset, hardware loads
1. The device is shipped with this option selected.
2. If 8 MHz 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.
Fuse can be programmed in order to divide the internal frequency by 8.
14CK + 4.1 ms to ensure programming mode can be entered.
Frequency Range (MHz)
Internal Calibrated RC Oscillator Operating Modes
Start-up times for the internal calibrated RC Oscillator clock selection
Oscillator Calibration Register – OSCCAL
CAL7
R/W
7
33.
7.3 - 8.1
301.
CAL6
R/W
6
Start-up Time from Power-
“Calibration Byte” on page
down and Power-save
CAL5
R/W
5
Device Specific Calibration Value
Reserved
6 CK
6 CK
6 CK
CAL4
R/W
4
“Oscillator Calibration Register – OSCCAL” on
CAL3
R/W
3
282.
AT90PWM2/3/2B/3B
CAL2
Additional Delay from
R/W
2
Reset (V
Table 26-1 on page
14CK + 65 ms
14CK + 4.1 ms
(1)(2)
CKSEL3..0
14CK
0010
CAL1
R/W
CC
1
(1)
= 5.0V)
(1)
CC
CAL0
R/W
), the CKDIV8
0
301.
SUT1..0
OSCCAL
00
01
10
11
33