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27
8210C–AVR–09/11
Atmel AVR XMEGA D
4.13
Register Descriptions – Fuses and Lockbits
4.13.1
FUSEBYTE1 – Fuse Byte1
• Bit 7:4 – WDWPER[3:0]: Watchdog Window Timeout Period
These fuse bits are used to set initial value of the closed window for the Watchdog Timer in Win-
dow Mode. During reset these fuse bits are automatically written to the WPER bits Watchdog
Window Mode Control Register. Refer to
”WINCTRL – Window Mode Control register” on page
for details.
• Bit 3:0 – WDPER[3:0]: Watchdog Timeout Period
These fuse bits are used to set the initial value of the watchdog timeout period. During reset
these fuse bits are automatically written to the PER bits in the watchdog control register. Refer to
”CTRL – Control register” on page 97
for details.
4.13.2
FUSEBYTE2 – Fuse Byte2
• Bit 7 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write
this bit to one when this register is written.
• Bit 6 – BOOTRST: Boot Loader Section Reset Vector
This fuse can be programmed so the reset vector is pointing to the first address in the boot
loader flash section. The device will then start executing from the boot loader flash section after
reset.
• Bit 5 – TOSCSEL: 32.768kHz Timer Oscillator Pin Selection
This fuse is used to select pin location for the 32.768kHz timer oscillator (TOSC). This fuse is
available on devices where XTAL and TOSC pins by default are shared.
Bit
7
6
5
4
3
2
1
0
+0x01
WDWPER[3:0]
WDPER[3:0]
FUSEBYTE1
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
+0x02
–
BOOTRST
TOSCSEL
–
–
–
BODPD[1:0]
FUSEBYTE2
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
1
1
1
1
1
1
1
1
Table 4-1.
Boot reset fuse.
BOOTRST
Reset Address
0
Reset vector = Boot loader reset
1
Reset vector = Application reset (address 0x0000)