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Basic Booting Process
24-18
ADSP-BF50x Blackfin Processor Hardware Reference
For normal boot operation, the target address points to RAM memory.
There are however a few exceptions where the target address can point to
on-chip or off-chip ROM. For example a zero-sized
BFLAG_INIT
block
would instruct the boot kernel to call a subroutine residing in ROM or
flash memory. This method is used to activate the CRC32 feature.
Byte Count
This 32-bit field tells the boot kernel how many bytes to process. Nor-
mally, this is the size of the payload data of a boot block. If the
BFLAG_FILL
flag is set there is no payload. In this case the
BYTE COUNT
field
uses the value in its
ARGUMENT
field to tell the boot kernel how many bytes
to process.
The byte count is a 32-bit value that should be divisible by four. Zero val-
ues are allowed in all block types. Most boot modes are based upon DMA
operation which are only 16-bit words for Blackfin processors. The boot
kernel may therefore start multiple DMA work units for large boot blocks.
This enables a single block to fill to zero the memory, for example, result-
ing in compact boot streams. The
HWAIT
signal may toggle for each work
unit.
If the
BFLAG_IGNORE
flag is set, the byte count is used to redirect the boot
source pointer to another memory location. In master boot modes, the
byte count is a two’s-complement (signed long integer) value. In slave
boot modes, the value must be positive.
Argument
This 32-bit field is a user variable for most block types. The value is acces-
sible by the initcode or the callback routine and can therefore be used for
optional instructions to these routines. When the CRC32 feature is acti-
vated, the
ARGUMENT
field holds the checksum over the payload of the
block.
Summary of Contents for EZ-KIT Lite ADSP-BF506F
Page 50: ...Contents l ADSP BF50x Blackfin Processor Hardware Reference ...
Page 92: ...Development Tools 1 30 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 110: ...Interface Overview 3 12 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 236: ...Internal Flash Memory Control Registers 6 92 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 650: ...Programming Examples 15 56 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 804: ...Programming Examples 17 92 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 1194: ...Programming Examples 24 90 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 1256: ...ACM Registers A 50 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 1264: ...Boundary Scan Architecture B 8 ADSP BF50x Blackfin Processor Hardware Reference ...