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<!-- Copyright (C) 2003 Red Hat, Inc.                                -->
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<HTML
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><HEAD
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>Linker Scripts</TITLE
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TITLE="eCos Reference Manual"
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TITLE="HAL Interfaces"
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><TR
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><TH
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>eCos Reference Manual</TH
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><TR
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><TD
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WIDTH="10%"
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ALIGN="left"
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><A
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HREF="hal-cache-control.html"
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ACCESSKEY="P"
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>Prev</A
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></TD
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><TD
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WIDTH="80%"
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ALIGN="center"
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VALIGN="bottom"
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>Chapter 9. HAL Interfaces</TD
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><TD
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WIDTH="10%"
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ALIGN="right"
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><A
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><DIV
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CLASS="SECTION"
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><H1
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CLASS="SECTION"
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><A
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NAME="HAL-LINKER-SCRIPTS">Linker Scripts</H1
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><P
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>When an eCos application is linked it must be done under the control
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of a linker script. This script defines the memory areas, addresses
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and sized, into which the code and data are to be put, and allocates
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the various sections generated by the compiler to these.</P
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><P
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>The linker script actually used is in
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<TT
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CLASS="FILENAME"
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>lib/target.ld</TT
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> in the install directory. This is
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actually manufactured out of two other files: a base linker script and
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an <TT
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CLASS="LITERAL"
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>.ldi</TT
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> file that was generated by the memory
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layout tool.</P
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><P
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>The base linker script is usually supplied either by the architecture
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HAL or the variant HAL. It consists of a set of linker script
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fragments, in the form of C preprocessor macros, that define the major
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output sections to be generated by the link operation. The
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<TT
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CLASS="LITERAL"
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>.ldi</TT
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> file, which is <TT
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CLASS="LITERAL"
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>#include'ed</TT
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>
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by the base linker script, uses these macro definitions to assign the
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output sections to the required memory areas and link addresses.</P
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><P
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>The <TT
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CLASS="LITERAL"
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>.ldi</TT
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> file is supplied by the platform HAL, and
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contains knowledge of the memory layout of the target platform. These
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files generally conform to a standard naming convention, each file
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being of the form:</P
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><P
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><TT
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CLASS="FILENAME"
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>pkgconf/mlt_&lt;architecture&gt;_&lt;variant&gt;_&lt;platform&gt;_&lt;startup&gt;.ldi</TT
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></P
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><P
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>where <TT
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CLASS="LITERAL"
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>&lt;architecture&gt;</TT
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>,
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<TT
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CLASS="LITERAL"
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>&lt;variant&gt;</TT
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> and
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<TT
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CLASS="LITERAL"
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>&lt;platform&gt;</TT
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> are the respective HAL package
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names and <TT
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CLASS="LITERAL"
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>&lt;startup&gt;</TT
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> is the startup type which
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is usually one of <TT
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CLASS="LITERAL"
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>ROM</TT
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>, <TT
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CLASS="LITERAL"
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>RAM</TT
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> or
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<TT
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CLASS="LITERAL"
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>ROMRAM</TT
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>.</P
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><P
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>In addition to the <TT
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CLASS="LITERAL"
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>.ldi</TT
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> file, there is also a
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congruously name <TT
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CLASS="LITERAL"
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>.h</TT
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> file. This may be used by the
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application to access information defined in the
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<TT
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CLASS="LITERAL"
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>.ldi</TT
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> file. Specifically it contains the memory
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layout defined there, together with any additional section names
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defined by the user. Examples of the latter are heap areas or PCI bus
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memory access windows.</P
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><P
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>The <TT
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CLASS="LITERAL"
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>.ldi</TT
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> is manufactured by the <SPAN
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CLASS="APPLICATION"
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>Memory
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Layout Tool</SPAN
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> (MLT). The <SPAN
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CLASS="APPLICATION"
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>MLT</SPAN
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> saves the memory
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configuration into a file named</P
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><P
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><TT
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CLASS="FILENAME"
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>include/pkgconf/mlt_&lt;architecture&gt;_&lt;variant&gt;_&lt;platform&gt;_&lt;startup&gt;.mlt</TT
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></P
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><P
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>in the platform HAL. This file is used by the
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<SPAN
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CLASS="APPLICATION"
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>MLT</SPAN
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> to manufacture both the
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<TT
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CLASS="LITERAL"
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>.ldi</TT
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> and <TT
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CLASS="LITERAL"
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>.h</TT
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> files. Users should
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beware that direct edits the either of these files may be overwritten
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if the <SPAN
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CLASS="APPLICATION"
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>MLT</SPAN
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> is run and regenerates them from the
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<TT
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CLASS="LITERAL"
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>.mlt</TT
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> file.</P
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><P
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>The names of the <TT
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CLASS="LITERAL"
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>.ldi</TT
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> and <TT
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CLASS="LITERAL"
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>.h</TT
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>
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files are defined by macro definitions in
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<TT
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CLASS="FILENAME"
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>pkgconf/system.h</TT
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>. These are
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<TT
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CLASS="LITERAL"
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>CYGHWR_MEMORY_LAYOUT_LDI</TT
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> and
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<TT
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CLASS="LITERAL"
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>CYGHWR_MEMORY_LAYOUT_H</TT
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> respectively. While there
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will be little need for the application to refer to the
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<TT
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CLASS="LITERAL"
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>.ldi</TT
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> file directly, it may include the
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<TT
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CLASS="LITERAL"
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>.h</TT
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> file as follows:</P
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><TABLE
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BORDER="5"
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BGCOLOR="#E0E0F0"
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WIDTH="70%"
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><TR
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><TD
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><PRE
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CLASS="PROGRAMLISTING"
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>#include CYGHWR_MEMORY_LAYOUT_H</PRE
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></TD
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></TR
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>Prev</A
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ALIGN="center"
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><A
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HREF="ecos-ref.html"
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>Home</A
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ALIGN="right"
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>Next</A
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></TD
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></TR
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><TR
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><TD
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WIDTH="33%"
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ALIGN="left"
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>Cache Control</TD
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><TD
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="hal-interfaces.html"
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ACCESSKEY="U"
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>Up</A
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></TD
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><TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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>Diagnostic Support</TD
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