Analog Devices ADSP-BF59x Blackfin, Hardware Reference Manual, Page: 648 / 772

Advanced Boot Techniques
16-26 ADSP-BF59x Blackfin Processor Hardware Reference
application can control the boot kernel behavior by setting the
BFLAG_WAKEUP
flag accordingly. See the
dFlags
variable on
Figure 16-25 on page 16-63 .
• The
BFLAG_QUICKBOOT
flag in the
BLOCK CODE
word of the block
header controls whether the current block is ignored for quick
boot.
If both the global
BFLAG_WAKEUP
and the block-specific
BFLAG_QUICKBOOT
flags are set, the boot kernel ignores those blocks. But since the
BFLAG_INIT
,
BFLAG_CALLBACK
,
BFLAG_FINAL,
and
BFLAG_AUX
flags are inter-
nally cleared and the
BFLAG_IGNORE
flag is toggled, through double
negation, the “ignore the ignore block” command instructs the boot ker-
nel to process the block.
Although the
BFLAG_INIT
flag is suppressed in quick boot, the user may
not want to combine the
BFLAG_INIT
flag with the
BFLAG_QUICKBOOT
flag.
The initialization code can interrogate the
BFLAG_WAKEUP
flag and execute
conditional instructions.
Indirect Booting
The processor’s boot kernel provides a control mechanism to let blocks
either boot directly to their final destination or load to an intermediate
storage place, then copy the data to the final destination in a second step.
This feature is motivated by the following requirements:
• Some boot modes do not use DMA. They load data by core
instruction. The core cannot access some memories directly (for
example L1 instruction SRAM), or is less efficient than the DMA
in accessing some memories.
• In some advanced booting scenarios, the core needs to access the
boot data during the booting process, for example in processing
decompression, decryption and checksum algorithms at boot time.