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<!-- Copyright (C) 2003 Red Hat, Inc.                                -->
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CLASS="SECTION"
><H1
CLASS="SECTION"
><A
NAME="HAL-INPUT-AND-OUTPUT">HAL I/O</H1
><P
>This section contains definitions for supporting access
to device control registers in an architecture neutral
fashion.</P
><P
>These definitions are normally found in the header file
<TT
CLASS="FILENAME"
>cyg/hal/hal_io.h</TT
>.  This file itself contains
macros that are generic to the architecture. If there are variant or
platform specific IO access macros then these will be found in
<TT
CLASS="FILENAME"
>cyg/hal/var_io.h</TT
> and
<TT
CLASS="FILENAME"
>cyg/hal/plf_io.h</TT
> in the variant or platform HALs
respectively. These files are include automatically by this header, so
need not be included explicitly.</P
><P
>This header (or more likely <TT
CLASS="FILENAME"
>cyg/hal/plf_io.h</TT
>) also
defines the PCI access macros. For more information on these see <A
HREF="pci-library-reference.html"
>the Section called <I
>PCI Library reference</I
> in Chapter 30</A
>.</P
><DIV
CLASS="SECTION"
><H2
CLASS="SECTION"
><A
NAME="AEN8057">Register address</H2
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>HAL_IO_REGISTER</PRE
></TD
></TR
></TABLE
><P
>This type is used to store the address of an I/O register. It will
normally be a memory address, an integer port address or an offset
into an I/O space. More complex architectures may need to code an
address space plus offset pair into a single word, or may represent it
as a structure.</P
><P
>Values of variables and constants of this type will usually be
supplied by configuration mechanisms or in target specific headers.</P
></DIV
><DIV
CLASS="SECTION"
><H2
CLASS="SECTION"
><A
NAME="AEN8062">Register read</H2
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
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><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>HAL_READ_XXX( register, value )
HAL_READ_XXX_VECTOR( register, buffer, count, stride )</PRE
></TD
></TR
></TABLE
><P
>These macros support the reading of I/O registers in various
sizes. The <TT
CLASS="REPLACEABLE"
><I
>XXX</I
></TT
> component of the name may be
<TT
CLASS="LITERAL"
>UINT8</TT
>, <TT
CLASS="LITERAL"
>UINT16</TT
>,
<TT
CLASS="LITERAL"
>UINT32</TT
>.</P
><P
><TT
CLASS="FUNCTION"
>HAL_READ_XXX()</TT
> reads the appropriately sized
value from the register and stores it in the variable passed as the
second argument.</P
><P
><TT
CLASS="FUNCTION"
>HAL_READ_XXX_VECTOR()</TT
> reads
<TT
CLASS="PARAMETER"
><I
>count</I
></TT
> values of the appropriate size into
<TT
CLASS="PARAMETER"
><I
>buffer</I
></TT
>. The <TT
CLASS="PARAMETER"
><I
>stride</I
></TT
>
controls how the pointer advances through the register space. A stride
of zero will read the same register repeatedly, and a stride of one
will read adjacent registers of the given size. Greater strides will
step by larger amounts, to allow for sparsely mapped registers for
example.</P
></DIV
><DIV
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><H2
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><A
NAME="AEN8077">Register write</H2
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>HAL_WRITE_XXX( register, value )
HAL_WRITE_XXX_VECTOR( register, buffer,count, stride )</PRE
></TD
></TR
></TABLE
><P
>These macros support the writing of I/O registers in various
sizes. The <TT
CLASS="REPLACEABLE"
><I
>XXX</I
></TT
> component of the name may be
<TT
CLASS="LITERAL"
>UINT8</TT
>, <TT
CLASS="LITERAL"
>UINT16</TT
>,
<TT
CLASS="LITERAL"
>UINT32</TT
>.</P
><P
><TT
CLASS="FUNCTION"
>HAL_WRITE_XXX()</TT
> writes
the appropriately sized value from the variable passed as the second argument
stored it in the register.</P
><P
><TT
CLASS="FUNCTION"
>HAL_WRITE_XXX_VECTOR()</TT
> writes
<TT
CLASS="PARAMETER"
><I
>count</I
></TT
> values of the appropriate size from <TT
CLASS="PARAMETER"
><I
>buffer</I
></TT
>. The <TT
CLASS="PARAMETER"
><I
>stride</I
></TT
> controls
how the pointer advances through the register space. A stride of
zero will write the same register repeatedly, and a stride of one
will write adjacent registers of the given size. Greater strides
will step by larger amounts, to allow for sparsely mapped registers
for example.</P
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