ATMEGA8-16AI datasheet(29/303 Pages) ATMEL

29 / 303 page

ATmega8(L)

2486M–AVR–12/03

Oscillator Calibration Register

– OSCCAL

• 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. During Reset, the 1 MHz calibration value

which is located in the signature row High byte (address 0x00) is automatically loaded

into the OSCCAL Register. If the internal RC is used at other frequencies, the calibration

values must be loaded manually. This can be done by first reading the signature row by

a programmer, and then store the calibration values in the Flash or EEPROM. Then the

value can be read by software and loaded into the OSCCAL Register. 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 0xFF 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 calibrate 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 1.0, 2.0, 4.0, or 8.0 MHz. Tuning to other values is

not guaranteed, as indicated in Table 11.

Bit

CAL7

CAL6

CAL5

CAL4

CAL3

CAL2

CAL1

CAL0

OSCCAL

Read/Write

R/W

Initial Value

Device Specific Calibration Value

Table 11. Internal RC Oscillator Frequency Range

OSCCAL Value

Min Frequency in Percentage of

Nominal Frequency (%)

Max Frequency in Percentage of

Nominal Frequency (%)

0x00

100

0x7F

150

0xFF

100

200

ATMEGA8-16AI Datasheet(PDF) 29 Page - ATMEL Corporation

ATMEGA8-16AI Datasheet(HTML) 29 Page - ATMEL Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL