User guide

6
Atmel AVR2054
8390B-AVR-12/11
Option
Common
bootloader
OTAU bootloader for Atmel
BitCloud applications
Bootloader for RF4CE
applications
BOOTSZ
Boot Flash
size=1024
words start
address=$F
C00
Boot Flash size=2048 words
start address=$F800
Boot Flash size=2048
words start address=$F800
BOOTRST Enabled Enabled Enabled
CKDIV8 Enabled Enabled Enabled
CKOUT Disabled Disabled Disabled
SUT_CKSE
L
Int. RC osc.;
Start-up
time: 6 CK +
65ms
Int. RC osc.; Start-up time: 6
CK + 65ms
Int. RC osc.; Start-up time:
6 CK + 0ms
Resulting
bytes
0xFF 0x9C
0x62
0xFF 0x9A 0x62 0xFE 0x92 0x42
Fuse bits configuration informs the MCU to start execution from the bootloader
section in memory instead of the application’s. On Atmel AVR microcontrollers the
bootloader is stored in the flash memory in the same address space as the
application. This reduces the amount of memory available for the application. The
fuse bits are also used to specify the amount of memory exclusively reserved for the
bootloader. Bootloader size may also vary depending on the bootloader type (for
example, the OTAU bootloader requires larger memory allocation than a bootloader
without OTAU support).
On XMEGAs, the embedded bootloader is kept in a separate storage, and so it is not
needed to specify the size of the bootloader section (all 256kb of flash are available
as the application memory).
Table 2-3. Fuse bits on Atmel ATxmega256A3 and Atmel ATxmega256D3.
Option Required value
JTAGUSERID 0xFF
WDWP 8 cycles (8ms @ 3.3V)
WDP 8 cycles (8ms @ 3.3V)
DVSDON OFF
BOOTRST
BOOTLDR
BODACT Disabled
BODPD Disabled
SUT 0ms
WDLOCK OFF
JTAGEN ON
EESAVE OFF
BODLVL 1.6V
Resulting bytes
FUSEBYTE0 0xFF
FUSEBYTE1 0x00