VisualDSP++ 4.5 Loader and Utilities Manual - Analog Devices

Blackfin Processor Booting
must perform the decompression on a compressed boot stream in a boot
process. The default initialization executable files with decompression
functions are included in VisualDSP++.
The loader -compression switch directs the loader utility to perform the
boot stream compression from the command line. VisualDSP++ also
offers a dedicated loader property page (see Figure 2-39) to manage the
compression from the IDDE.
The loader utility takes two steps to compress a boot stream. First, the
utility generates the boot stream in the conventional way (builds data
blocks), then applies the compression to the boot stream. The decompression
initialization is the reversed process: the loader utility decompresses
the compressed stream first, then loads code and data into memory segments
in the conventional way.
The loader utility compresses the boot stream on the .dxe-by-.dxe basis.
For each input .dxe file, the utility compresses the code and data together,
including all code and data from any associated overlay (.ovl) and shared
memory (.sm) files.
Compressed Streams
Figure 2-33 illustrates the basic structure of a loader file with compressed
streams.
The initialization code is on the top of the loader file. The initialization
code is loaded into the processor first and is executed first when a boot
process starts. Once the initialization code is executed, the rest of the
stream is brought into the processor. The initialization code calls the
decompression routine to perform the decompression operation on the
stream, and then loads the decompressed stream into the processor’s memory
in the same manner a conventional boot kernel does when it
encounters a compressed stream. Finally, the loader utility loads the
uncompressed boot stream in the conventional way.
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