User guide

Atmel AVR2054: Serial Bootloader User Guide [APPLICATION NOTE]
8390D−WIRELESS−03/2015
9
Table 2-2. Fuse bits on ATmega1281, ATmega128RFA1 and ATmega256(4)RFR2 .
Option Common bootloader Bootloader for RF4CE
applications
BODLEVEL Disabled Brown-
out detection at
VCC = 1.8V
OCDEN
Disabled
Disabled
JTAGEN
Enabled
Enabled
SPIEN
Enabled
Enabled
WDTON
Disabled
Disabled
EESAVE
Disabled
Enabled
BOOTSZ Boot Flash size=1024
words start
address=$FC00
Boot Flash size=2048
words start
address=$F800
BOOTRST
Enabled
Enabled
CKDIV8
Enabled
Enabled
CKOUT
Disabled
Disabled
SUT_CKSEL Int. RC osc.; Start-
up time: 6 CK + 65ms
Int. RC osc.; Start-
up
time: 6 CK + 0ms
Resulting
fuse bytes
0xFF 0x9C 0x62 0xFE 0x92 0x42
For fuse settings in BitCloud OTA configurations see Apendix of [4].
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