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<!-- Copyright (C) 2003 Red Hat, Inc.                                -->
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><H1
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NAME="HAL-GENERAL-PRINCIPLES">Chapter 8. General principles</H1
><P
>The HAL has been implemented according to the following general
principles:</P
><P
></P
><OL
TYPE="1"
><LI
><P
>             The HAL is implemented in C and assembler, although the
              eCos kernel is largely implemented in C&#0043;&#0043;.
              This is to permit the HAL the widest possible
              applicability.</P
></LI
><LI
><P
>All interfaces to the HAL are implemented by
              CPP macros. This allows them to be implemented as inline
              C code, inline assembler or function calls to external C
              or assembler code. This allows the most efficient
              implementation to be selected without affecting the
              interface. It also allows them to be redefined if the
              platform or variant HAL needs to replace or enhance a definition
              from the architecture HAL.</P
></LI
><LI
><P
>The HAL provides simple, portable mechanisms for dealing
with the hardware of a wide range of architectures and platforms.
It is always possible to bypass the HAL and program the hardware
directly, but this may lead to a loss of portability. </P
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1	28	unneback	`<!-- Copyright (C) 2003 Red Hat, Inc. -->`
2			`<!-- This material may be distributed only subject to the terms -->`
3			`<!-- and conditions set forth in the Open Publication License, v1.0 -->`
4			`<!-- or later (the latest version is presently available at -->`
5			`<!-- http://www.opencontent.org/openpub/). -->`
6			`<!-- Distribution of the work or derivative of the work in any -->`
7			`<!-- standard (paper) book form is prohibited unless prior -->`
8			`<!-- permission is obtained from the copyright holder. -->`
9			`<HTML`
10			`><HEAD`
11			`><TITLE`
12			`>General principles</TITLE`
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15			`NAME="GENERATOR"`
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18			`REL="HOME"`
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21			`REL="UP"`
22			`TITLE="The eCos Hardware Abstraction Layer (HAL)"`
23			`HREF="the-ecos-hardware-abstraction-layer.html"><LINK`
24			`REL="PREVIOUS"`
25			`TITLE="Architecture, Variant and Platform"`
26			`HREF="hal-architecture-variant-and-platform.html"><LINK`
27			`REL="NEXT"`
28			`TITLE="HAL Interfaces"`
29			`HREF="hal-interfaces.html"></HEAD`
30			`><BODY`
31			`CLASS="CHAPTER"`
32			`BGCOLOR="#FFFFFF"`
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49			`>eCos Reference Manual</TH`
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52			`><TD`
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54			`ALIGN="left"`
55			`VALIGN="bottom"`
56			`><A`
57			`HREF="hal-architecture-variant-and-platform.html"`
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59			`>Prev</A`
60			`></TD`
61			`><TD`
62			`WIDTH="80%"`
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79			`WIDTH="100%"></DIV`
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81			`CLASS="CHAPTER"`
82			`><H1`
83			`><A`
84			`NAME="HAL-GENERAL-PRINCIPLES">Chapter 8. General principles</H1`
85			`><P`
86			`>The HAL has been implemented according to the following general`
87			`principles:</P`
88			`><P`
89			`></P`
90			`><OL`
91			`TYPE="1"`
92			`><LI`
93			`><P`
94			`> The HAL is implemented in C and assembler, although the`
95			`eCos kernel is largely implemented in C++.`
96			`This is to permit the HAL the widest possible`
97			`applicability.</P`
98			`></LI`
99			`><LI`
100			`><P`
101			`>All interfaces to the HAL are implemented by`
102			`CPP macros. This allows them to be implemented as inline`
103			`C code, inline assembler or function calls to external C`
104			`or assembler code. This allows the most efficient`
105			`implementation to be selected without affecting the`
106			`interface. It also allows them to be redefined if the`
107			`platform or variant HAL needs to replace or enhance a definition`
108			`from the architecture HAL.</P`
109			`></LI`
110			`><LI`
111			`><P`
112			`>The HAL provides simple, portable mechanisms for dealing`
113			`with the hardware of a wide range of architectures and platforms.`
114			`It is always possible to bypass the HAL and program the hardware`
115			`directly, but this may lead to a loss of portability. </P`
116			`></LI`
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157			`></TR`
158			`><TR`
159			`><TD`
160			`WIDTH="33%"`
161			`ALIGN="left"`
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163			`>Architecture, Variant and Platform</TD`
164			`><TD`
165			`WIDTH="34%"`
166			`ALIGN="center"`
167			`VALIGN="top"`
168			`><A`
169			`HREF="the-ecos-hardware-abstraction-layer.html"`
170			`ACCESSKEY="U"`
171			`>Up</A`
172			`></TD`
173			`><TD`
174			`WIDTH="33%"`
175			`ALIGN="right"`
176			`VALIGN="top"`
177			`>HAL Interfaces</TD`
178			`></TR`
179			`></TABLE`
180			`></DIV`
181			`></BODY`
182			`></HTML`
183			`>`

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[/] [openrisc/] [trunk/] [rtos/] [ecos-2.0/] [doc/] [html/] [ref/] [hal-general-principles.html] - Blame information for rev 28