attiny11 ATMEL Corporation, attiny11 Datasheet - Page 12

• Manufacturer Part Number: attiny11
• Description: 8-bit Microcontroller With 1k Byte Flash
• Manufacturer: ATMEL Corporation

Register Description
Oscillator Calibration Register
– OSCCAL
12
ATtiny11/12
• Bits 7..0 - CAL7..0: Oscillator Calibration Value
Writing the calibration byte to this address will trim the internal oscillator to remove pro-
cess variations from the oscillator frequency. When OSCCAL is zero, the lowest
available frequency is chosen. Writing non-zero values to this register will increase the
frequency of the internal oscillator. Writing $FF to the register gives the highest available
frequency. The calibrated oscillator is used to time EEPROM access. If EEPROM is
written, do not calibrate to more than 10% above the nominal frequency. Otherwise, the
EEPROM write may fail. Table 4 shows the range for OSCCAL. Note that the oscillator
is intended for calibration to 1.2 MHz, thus tuning to other values is not guaranteed.
Table 4. Internal RC Oscillator Frequency Range
Bit
$31
Read/Write
Initial Value
OSCCAL Value
$7F
$FF
$00
CAL7
R/W
7
0
CAL6
R/W
6
0
CAL5
R/W
5
0
Min Frequency
CAL4
R/W
0.6 MHz
0.8 MHz
1.2 MHz
4
0
CAL3
R/W
3
0
CAL2
R/W
2
0
CAL1
R/W
1
0
Max Frequency
1.2 MHz
1.7 MHz
2.5 MHz
CAL0
R/W
0
0
1006F–AVR–06/07
OSCCAL