126
8331B–AVR–03/12
Atmel AVR XMEGA AU
This bit is protected by the Configuration Change Protection mechanism. For a detailed descrip-
tion, refer to ”Configuration Change Protection” on page 13.
10.6.2 STATUS: Status register
• Bit 7 – BBPWR: Battery Backup Power
This flag is set if no power is detected on the V
BAT
pin when the device leaves reset. The flag
can be cleared by writing a one to this bit location.
• Bit 6:4 – 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 – XOSCRDY: Crystal Oscillator Ready
This flag is set when the 32.678kHz crystal oscillator has started and is stable and ready. The
flag can be cleared by applying a reset to the battery backup system. The actual start-up time is
crystal dependent. Refer to the datasheet for the crystal oscillator used for more information.
• Bit 2 – XOSCFAIL: Crystal Oscillator Failure
This flag is set if a crystal oscillator failure is detected. The flag can be cleared by writing a one
to this bit location or by applying a reset to the battery backup system.
• Bit 1 – BBBODF: Battery Backup Brown-out Detection Flag
This flag is set if battery backup BOD is detected when the battery backup system is powered
from the V
BAT
pin. The flag can be cleared by writing a one to this bit location. This flag is not
valid when BBPWR is set.
• Bit 0 – BBPODF: Battery Backup Power-on Detection Flag
This flag is set if battery backup power-on is detected; i.e., when power is connected to the V
BAT
pin. The flag is updated only during device startup when main power is applied. Applying or
reapplying power to the V
BAT
pin while main power is present will not change this flag until main
power is removed and re-applied. The flag can be cleared by writing a one to this bit location.
This flag is not valid when BBPWR is set.
10.6.3 BACKUP0: Backup register 0
Bit 76543210
+0x01
BBPWR – – – XOSCRDY XOSCFAIL BBBODF BBPODF STATUS
Read/Write R/W R R R R/W R/W R/W R/W
Initial Value 0 0 0 0 x x 0 0
Bit 76543210
+0x02
BACKUP0[7:0] BACKUP0
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Valuexxxxxxxx
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