В каких конкретно примерах програм? В апноте "AVR1300 Using the XMega ADC" есть обнуление NVM.CMD. http://www.microchip.com//wwwAppNotes/AppNotes.aspx?appnote=en591303
#include <ioavr.h>
; ---
; This routine reads the calibration byte given by the index in R16.
;
; Input:
; R16 - Byte index.
;
; Returns:
; R16 - Calibration byte.
; ---
MODULE _SP_ReadCalibrationByte
PUBLIC SP_ReadCalibrationByte
RSEG CODE
SP_ReadCalibrationByte:
ldi r20, NVM_CMD_READ_CALIB_ROW_gc ; Prepare NVM command in R20.
mov ZL, r16 ; Load byte index into low byte of Z.
clr ZH ; Clear high byte of Z.
sts NVM_CMD, r20 ; Load prepared command into NVM Command register.
lpm r16, Z ; Preform a LPM to read out byte to R16
ldi r20, NVM_CMD_NO_OPERATION_gc ; Clear NVM Command register
sts NVM_CMD, r20
ret
ENDMOD
END