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Chapter 7
Secure self-
programming
Boot block cluster
Number of boot
blocks
280
The boot cluster swapping function enables secure self-programming. In case
the boot code shall be rewritten, the new code can be written to the inactive
boot block cluster, while the boot_flag remains in its previous state.
If rewriting of the boot block cluster has been completed successfully, the
boot_flag can be inverted, making the new boot code active.
If rewriting of the new boot code fails for any reason, e.g. power fail or
unintended reset, the old boot code still remains active and rewriting can be
started again.
The boot code size itself may be smaller than the boot swap cluster size.
The number of flash memory blocks, which are part of the boot code, are
named boot block cluster. The number of boot blocks, which are member of the
cluster, can be defined during self-programming via the self-programming
library.
The boot block cluster size determines the boot swap cluster size. This is
automatically evaluated from the number of boot blocks, defined during self-
programming.
Table 7-10 on page 281 shows the relation between the number of boot blocks,
the boot block cluster size and the boot swap cluster.
The numer of boot blocks has to be defined by the user during
self-programming. It determines the blocks, which are subject to the boot block
cluster protection, that allows to protect the boot blocks from any erase or write
process.
User's Manual U18743EE1V2UM00
Flash Memory
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