VisualDSP++ 4.5 Loader and Utilities Manual - Analog Devices

Loader/Splitter for Blackfin Processors
Table 2-7. ADSP-BF561/BF566 Global Header Structure (Cont’d)
Bit Field Description
8–10 Baud rate for SPI boot: 00 = 500k, 01 = 1M, 10 = 2M
11–27 Reserved for future use
28–31 Signature that indicates valid boot stream
Following the global header is a .dxe count block, which contains a 32-bit
byte count for the first .dxe file in the boot stream. Though this block
contains only a byte count, it is encapsulated by a 10-byte block header,
just like the other blocks.
The 10-byte header instructs the boot ROM where, in memory, to place
each block, how many bytes to copy, and whether the block needs any
special processing. The block header structure is the same as that of the
ADSP-BF531/BF532/BF533 processors (described in
“ADSP-BF531/BF532/BF533/BF534/BF536/BF537/BF538/ BF539
Blocks, Block Headers, and Flags” on page 2-33). Each header contains a
4-byte start address for the data block, a 4-byte count for the data block,
and a 2-byte flag word, indicating whether the data block is a “zero-fill”
block or a “final block” (the last block in the boot stream).
For the .dxe count block, the address field is irrelevant since the block is
not going to be copied to memory. The “ignore bit” is set in the flag word
of this header, so the boot loader utility does not try to load the .dxe
count but skips the count. For more details, see
“ADSP-BF531/BF532/BF533/BF534/BF536/BF537/BF538/ BF539
Blocks, Block Headers, and Flags” on page 2-33.
Following the .dxe count block are the rest of the blocks of the first .dxe.
A bit-by-bit description of the boot steam is presented in Table 2-8.
When learning about the ADSPP-BF561/BF566 boot stream structure,
keep in mind that the count byte for each .dxe is, itself, a block encapsulated
by a block header.
VisualDSP++ 4.5 Loader and Utilities Manual 2-45