Rainbow-electronics Atmega169L Manuel d'utilisateur télécharger pdf (Page 28)

ATmega169V/L

2514A–AVR–08/02

Oscillator Calibration Register

– OSCCAL

• 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 MHz. Tuning to

other values is not guaranteed, as indicated in Table 10.

Bit 76543210

– CAL6 CAL5 CAL4 CAL3 CAL2 CAL1 CAL0 OSCCAL

Read/Write R R/W R/W R/W R/W R/W R/W R/W

Initial Value Device Specific Calibration Value

Table 10. Internal RC Oscillator Frequency Range.

OSCCAL Value

Min Frequency in Percentage of

Nominal Frequency

Max Frequency in Percentage of

Nominal Frequency

0x00 50% 100%

0x3F 75% 150%

0x7F 100% 200%

1 2 ... 23 24 25 26 27 28 29 30 31 32 33 ... 316 317

Pas de commentaire

Rainbow-electronics Atmega169L Manuel d'utilisateur Page 28