Datasheet

13.12.1 Oscillator Calibration Register

Name: OSCCAL

Offset: 0x66

Reset: Device Specific Calibration Value

Property: -

Bit 7 6 5 4 3 2 1 0

CAL[7:0]

Access

R/W R/W R/W R/W R/W R/W R/W R/W

Reset x x x x x x x x

Bits 7:0 – CAL[7:0] Oscillator Calibration Value

The oscillator calibration register is used to trim the calibrated internal RC oscillator to remove process

variations away from the oscillator frequency. A preprogrammed calibration value is automatically written

to this register during chip reset, giving the factory calibrated frequency as specified in the Clock

Characteristics section of chapter Electrical Characteristics.The application software can write this

the Clock Characteristics section of chapter Electrical Characteristics. Calibration outside that range is not

recommended.

Note that this oscillator is used to time EEPROM and Flash write accesses, and these write times will be

affected accordingly. If the EEPROM or Flash are written, do not calibrate to more than 8.8 MHz.

Otherwise, the EEPROM or Flash write may fail.

The CAL7 bit determines the range of operation for the oscillator. Setting this bit to 0 gives the lowest

frequency range, setting this bit to 1 gives the highest frequency range. The two frequency ranges are

overlapping, in other words, a setting of OSCCAL=0x7F gives a higher frequency than OSCCAL=0x80.

The CAL[6:0] bits are used to tune the frequency within the selected range. A setting of 0x00 gives the

lowest frequency in that range and a setting of 0x7F gives the highest frequency in the range.