ATTIny2313-16MI ATMEL Corporation, ATTIny2313-16MI Datasheet - Page 26

• Manufacturer Part Number: ATTIny2313-16MI
• Description: 8-bit AVR Microcontroller with 2K Bytes In-System Programmable Flash
• Manufacturer: ATMEL Corporation

Oscillator Calibration Register
– OSCCAL
26
ATtiny2313/V
When this Oscillator is selected, start-up times are determined by the SUT Fuses as
shown in Table 7.
Table 7. Start-up times for the internal calibrated RC Oscillator clock selection
Note:
• Bits 6..0 – CAL6..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. This is done automatically during Chip
Reset. 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
0x7F to the register gives the highest available frequency. The calibrated Oscillator is
used to time EEPROM and Flash access. If EEPROM or Flash is written, do not cali-
brate to more than 10% above the nominal frequency. Otherwise, the EEPROM or Flash
write may fail. Note that the Oscillator is intended for calibration to 8.0/4.0 MHz. Tuning
to other values is not guaranteed, as indicated in Table 8.
Avoid changing the calibration value in large steps when calibrating the Calibrated Inter-
nal RC Oscillator to ensure stable operation of the MCU. A variation in frequency of
more than 2% from one cycle to the next can lead to unpredictable behavior. Changes in
OSCCAL should not exceed 0x20 for each calibration.
Table 8. Internal RC Oscillator Frequency Range.
Bit
Read/Write
Initial Value
SUT1..0
OSCCAL Value
10
00
01
11
(1)
0x3F
0x7F
0x00
1. The device is shipped with this option selected.
Start-up Time from Power-
down and Power-save
R
7
–
Min Frequency in Percentage of
6 CK
6 CK
6 CK
CAL6
R/W
6
Nominal Frequency
CAL5
R/W
100%
5
50%
75%
Device Specific Calibration Value
CAL4
R/W
4
Additional Delay from
Reset (V
Reserved
14CK + 4.1 ms
14CK + 65 ms
CAL3
R/W
3
14CK
CC
= 5.0V)
Max Frequency in Percentage of
CAL2
R/W
2
Nominal Frequency
CAL1
R/W
Recommended Usage
BOD enabled
Fast rising power
Slowly rising power
1
100%
150%
200%
CAL0
R/W
0
2543C–AVR–12/03
OSCCAL