99
8331B–AVR–03/12
Atmel AVR XMEGA AU
7.10.4 XOSCFAIL – XOSC Failure Detection register
• Bit 7:4 – 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 3 – PLLFDIF: PLL Fault Detection Flag
If PLL failure detection is enabled, PLLFDIF is set when the PLL looses lock. Writing logic one to
this location will clear PLLFDIF.
• Bit 2 – PLLFDEN: PLL Fault Detection Enable
Setting this bit will enable PLL failure detection. A non-maskable interrupt will be issued when
PLLFDIF is set.
This bit is protected by the configuration change protection mechanism. Refer to ”Configuration
Change Protection” on page 13 for details.
• Bit 1 – XOSCFDIF: Failure Detection Interrupt Flag
If the external clock source oscillator failure monitor is enabled, XOSCFDIF is set when a failure
is detected. Writing logic one to this location will clear XOSCFDIF.
• Bit 0 – XOSCFDEN: Failure Detection Enable
Setting this bit will enable the failure detection monitor, and a non-maskable interrupt will be
issued when XOSCFDIF is set.
This bit is protected by the configuration change protection mechanism. Refer to ”Configuration
Change Protection” on page 13 for details. Once enabled, failure detection can only be disabled
by a reset.
7.10.5 RC32KCAL – 32kHz Oscillator Calibration register
• Bit 7:0 – RC32KCAL[7:0]: 32.768kHz Internal Oscillator Calibration Register
This register is used to calibrate the 32.768kHz internal oscillator. A factory-calibrated value is
loaded from the signature row of the device and written to this register during reset, giving an
oscillator frequency close to 32.768kHz. The register can also be written from software to cali-
brate the oscillator frequency during normal operation.
Bit 765432 1 0
+0x03 – – – – PLLFDIF PLLFDEN XOSCFDIF XOSCFDEN XOSCFAIL
Read/Write R R R R R/W R/W R/W R/W
Initial Value000000 0 0
Bit 76543210
+0x04 RC32KCAL[7:0] RC32KCAL
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Valuexxxxxxxx
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