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VisualDSP++ 4.5 Loader and Utilities Manual - Analog Devices

VisualDSP++ 4.5 Loader and Utilities Manual - Analog Devices

VisualDSP++ 4.5 Loader and Utilities Manual - Analog Devices

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Blackfin Processor Booting<br />

Booting Compressed Streams<br />

The Figure 2-37 shows the booting sequence of a loader file with compressed<br />

streams. The loader file is pre-stored in the flash memory.<br />

1. The boot ROM is pointing to the start of the flash memory. The<br />

boot ROM reads the initialization code header <strong>and</strong> boots the initialization<br />

code.<br />

2. The boot ROM jumps to <strong>and</strong> starts executing the initialization<br />

code.<br />

3. (A) The initialization code scans the header for any compressed<br />

streams (see the compression flag structure in Figure 2-36). The<br />

code decompresses the streams to the decompression window (in<br />

parts) <strong>and</strong> runs the initialization kernel on the decompressed data.<br />

(B) The initialization kernel boots the data into various memories<br />

just as the boot ROM kernel does.<br />

4. The initialization code sets the boot ROM to boot the uncompressed<br />

blocks <strong>and</strong> the final block (FINAL flag is set in the block<br />

header’s flag word). The boot ROM boots the final payload, overwriting<br />

any areas used by the initialization code. Because the final<br />

flag is set in the header, the boot ROM jumps to EVT1<br />

(0xffa00000) to start application code execution.<br />

Decompression Initialization Files<br />

As stated before, a decompression initialization .dxe file must be used<br />

when building a loader file with compressed streams. The decompression<br />

initialization .dxe file has a built-in decompression engine to decompress<br />

the compressed streams from the loader file.<br />

The decompression initialization file can be specified from the loader<br />

property page or from the loader comm<strong>and</strong> line via the -init filename.dxe<br />

switch. <strong>VisualDSP++</strong> includes the default decompression initialization<br />

2-60 <strong>VisualDSP++</strong> <strong>4.5</strong> <strong>Loader</strong> <strong>and</strong> <strong>Utilities</strong> <strong>Manual</strong>

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