User`s guide

B.8 Special ROM Header
Table B–5 describes each entry in the special header.
Table B–5 Special Header Entry Descriptions
Entry Description
Validation and inverse
validation pattern
This quadword contains a special signature pattern used to
validate that the special ROM header has been located. The
pattern is 5A5AC3C3A5A53C3C.
Header size (bytes) This longword provides the size of the header block, which
varies among versions of the header specification.
When the header is located, SROM code determines where
the image begins based on the header size. Additional data
added to the header is ignored by older SROM code.
A header size of 32 bytes implies version 0 of the header
specifications.
Image checksum This longword is used to verify the integrity of the ROM.
Image size The image size is used by the SROM code to determine how
much of the system flash ROM should be loaded.
Decompression flag The decompression flag informs the SROM code whether
the MAKEROM tool was used to compress the ROM image
with a repeating byte algorithm. The SROM code contains
routines that execute the decompression algorithm. Other
compression and decompression schemes, which work
independently from this scheme, may be employed.
Destination address This quadword contains the destination address for the
image. The SROM code loads the image at this address and
begins execution.
Header revision The revision of the header specification used in this header.
This is necessary to provide for changes to the header
specification. Version 0 headers are identified by the size of
the header (32 bytes).
Flash ROM image size The flash ROM image size reflects the size of the image as
it is contained in the flash ROM.
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B–10 SROM Initialization