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Each processor type may have a different compiler (linker) output format, and some processor types may have a ROM-ed embedded boot-loader (firmware), with its own requirements on the download format. The SynDEx common download format encapsulates the details and the differences of the compiler output formats, and of the boot-loaders download formats; it is composed as follows:
- four bytes prefix encoding the 32 bits big-endian total length of the following sequence of bytes
- sequence of bytes, encoding one complete executive, structured as required by the destination boot-loader, and padded if needed with null bytes until the total length is a multiple of four.
The first executive forwarded to a descendant being received by that descendant's boot-loader, that executive must be sent WITHOUT its four bytes prefix; the following executives sent to the same descendant being forwarded by that descendant's executive, they must be sent WITH their four bytes prefix.
The sequence of bytes itself must follow the format expected by the destination boot-loader. Therefore a linker post-processor must be developped for each processor type, to translate the linker output file into the SynDEx common dowload format described above. All the post-processors' outputs will be concatenated by the makefile into a unique contiguous image (file), that the root executive will use as source.
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Up: SynDEx Downloader Specification
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Julien Forget
2003-03-21