FUJITSU MB91460 SERIES FR60 - Manual (Page 1007)

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Chapter 53 Fixed Mode-Reset Vector / BOOT-ROM
5.Bootloader Update Strategy
By use of this bootloader the application as well as user bootloader 2 can be re-programmed.
If you want to re-program user bootloader 1, then functions in user bootloader 2 have to be called to erase the
sector where user bootloader 1 and the Magic Number are located. After erasing, program the new user
bootloader to the section. As last step, the Magic Number should be set to 0x000A897A.
This procedure guarantees that there is started always a valid bootloader. If after erasing or during programming
user bootloader 1 a reset or a power-down occurs, user bootloader 2 is started and the programming can be
resumed.