Atmel XMEGA B, User Manual

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94 XMEGA B [DATASHEET]
8291B–AVR–01/2013

Bit 7 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero when this
register is written.

Bit 6:0 – CALA[6:0]: DFLL Calibration bits
These bits hold the part of the oscillator calibration value that is used for automatic runtime calibration. A factory-
calibrated value is loaded from the signature row of the device and written to this register during reset, giving an oscillator
frequency approximate to the nominal frequency for the oscillator. The bits cannot be written when the DFLL is enabled.
7.11.3 CALB – Calibration register B

Bit 7:6 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to zero
when this register is written.

Bit 5:0 – CALB[5:0]: DFLL Calibration bits
These bits hold the part of the oscillator calibration value that is used to select the oscillator frequency. A factory-
calibrated value is loaded from the signature row of the device and written to this register during reset, giving an oscillator
frequency approximate to the nominal frequency for the oscillator. These bits are not changed during automatic run-time
calibration of the oscillator. The bits cannot be written when the DFLL is enabled. When calibrating to a frequency
different from the default, the CALA bits should be set to a middle value to maximize the range for the DFLL.
Bit 7 6 5 4 3 2 1 0
+0x03
– – CALB[5:0]
Read/Write R R R/W R/W R/W R/W R/W R/W
Initial Value 0 0 x x x x x x