introduction.sgml

开放源码实时操作系统源码.

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<!--     eCos User Guide                                             -->
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<!-- Copyright (C) 2003 Nick Garnett                                 -->
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<part ID="user-guide-introduction">
<TITLE>Introduction</TITLE>

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<chapter ID="FOREWORD-WHATS-NEW">
<TITLE>What's New?</TITLE>

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<chapter ID="ecos-key-features">
<TITLE>Key Features</TITLE>

<itemizedlist>

<listitem>
<para><productname>eCos</productname> is distributed under the GPL
license with an exception which permits proprietary application code
to be linked with <productname>eCos</productname> without itself being
forced to be released under the GPL. It is also royalty and buyout
free.
</para>
</listitem>

<listitem>
<para>As an Open Source project, <productname>eCos</productname> is
under constant improvement, with an active developer community, based
around the <productname>eCos</productname> web site at <ULINK
URL="http://ecos.sourceware.org/">http://ecos.sourceware.org/</ULINK>.
</para>
</listitem>

<listitem>
<para>Powerful GUI-based configuration system allowing both large and
fine grained configuration of <productname>eCos</productname>. This
allows the functionality of <productname>eCos</productname> to be
customized to the exact requirements of the application.
</para>
</listitem>

<listitem>
<para>Full-featured, flexible, configurable, real time embedded
kernel. The kernel provides thread scheduling, synchronization,
timer, and communication primitives. It handles hardware resources
such as interrupts, exceptions, memory and caches.
</para>
</listitem>

<listitem>
<para>The Hardware Abstraction Layer (HAL) hides the specific features
of each supported CPU and platform, so that the kernel and other
run-time components can be implemented in a portable fashion.
</para>
</listitem>

<listitem>
<para>Support for &micro;ITRON and POSIX Application Programmer
Interfaces (APIs). It also includes a fully featured, thread-safe ISO
standard C library and math library.
</para>
</listitem>

<listitem>
<para>Support for a wide variety of devices including many serial
devices, ethernet controllers and FLASH memories. There is also
support for PCMCIA, USB and PCI interconnects.
</para>
</listitem>

<listitem>
<para>A fully featured TCP/IP stack implementing IP, IPv6, ICMP, UDP
and TCP over ethernet. Support for SNMP, HTTP, TFTP and FTP are also
present.
</para>
</listitem>

<listitem>
<para>The RedBoot ROM monitor is an application that uses the
<productname>eCos</productname> HAL for portability. It provides
serial and ethernet based booting and debug services during
development.
</para>
</listitem>

<listitem>
<para>Many components include test programs that validate the
components behaviour. These can be used both to check that hardware is
functioning correctly, and as examples of
<productname>eCos</productname> usage.
</para>
</listitem>

<listitem>
<para><productname>eCos</productname> documentation included this User
Guide, the Reference Manual and the Components Writer's Guide. These
are being continually updated as the system develops.
</para>
</listitem>

</itemizedlist>

</chapter>

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<chapter ID="ecos-overview">
<TITLE><productname>eCos</productname> Overview</TITLE>

<PARA><productname>eCos</productname> is an open source, configurable,
	portable, and royalty-free embedded real-time operating
	system. The following text expands on these core aspects that
	define <productname>eCos</productname>.</PARA>

<PARA><productname>eCos</productname> is provided as an open source
	runtime system supported by the GNU open source development
	tools. Developers have full and unfettered access to all
	aspects of the runtime system. No parts of it are proprietary
	or hidden, and you are at liberty to examine, add to, and
	modify the code as you deem necessary. These rights are
	granted to you and protected by the GNU Public License (GPL).
	An exception clause has been added to the eCos license which
	limits the circumstances in which the license applies to other
	code when used in conjunction with eCos. This exception grants
	you the right to freely develop and distribute applications
	based on <productname>eCos</productname>. You are not expected
	or required to make your embedded applications or any
	additional components that you develop freely available so
	long as they are not derived from
	<productname>eCos</productname> code. We of course welcome all
	contributions back to <productname>eCos</productname> such as
	board ports, device drivers and other components, as this
	helps the growth and development of
	<productname>eCos</productname>, and is of benefit to the
	entire <productname>eCos</productname> community. See <XREF
	LINKEND="ecos-licensing"> for more details.</PARA>

<PARA>One of the key technological innovations in
	<productname>eCos</productname> is the configuration
	system. The configuration system allows the application writer
	to impose their requirements on the run-time components, both
	in terms of their functionality and implementation, whereas
	traditionally the operating system has constrained the
	application's own implementation. Essentially, this enables
	<productname>eCos</productname> developers to create their own
	application-specific operating system and makes
	<productname>eCos</productname> suitable for a wide range of
	embedded uses. Configuration also ensures that the resource
	footprint of <productname>eCos</productname> is minimized as
	all unnecessary functionality and features are removed. The
	configuration system also presents
	<productname>eCos</productname> as a component
	architecture. This provides a standardized mechanism for
	component suppliers to extend the functionality of
	<productname>eCos</productname> and allows applications to be
	built from a wide set of optional configurable run-time
	components. Components can be provided from a variety of
	sources including: the standard
	<productname>eCos</productname> release; commercial third
	party developers or open source contributors.</PARA>

<PARA>The royalty-free nature of <productname>eCos</productname> means that you can develop and
deploy your application using the standard <productname>eCos</productname> release without
incurring any royalty charges. In addition, there are no up-front
license charges for the <productname>eCos</productname> runtime source code and associated
tools. We provide, without charge, everything necessary for basic
embedded applications development.</PARA>

<PARA><productname>eCos</productname> is designed to be portable to a
wide range of target architectures and target platforms including 16,
32, and 64 bit architectures, MPUs, MCUs and DSPs. The
<productname>eCos</productname> kernel, libraries and runtime
components are layered on the Hardware Abstraction Layer (HAL), and
thus will run on any target once the HAL and relevant device drivers
have been ported to the target's processor architecture and
board. Currently <productname>eCos</productname> supports a large
range of different target architectures:
 </para>

<itemizedlist>

<listitem><para>ARM, Intel StrongARM and XScale</para></listitem>

<listitem><para>Fujitsu FR-V</para></listitem>

<listitem><para>Hitachi SH2/3/4</para></listitem>

<listitem><para>Hitachi H8/300H </para></listitem>

<listitem><para>Intel x86</para></listitem>

<listitem><para>MIPS</para></listitem>

<listitem><para>Matsushita AM3x</para></listitem>

<listitem><para>Motorola PowerPC</para></listitem>

<listitem><para>Motorola 68k/Coldfire</para></listitem>

<listitem><para>NEC V850</para></listitem>

<listitem><para>Sun SPARC</para></listitem>

</itemizedlist>

<para>
including many of the popular variants of these architectures
and evaluation boards.</PARA>

<PARA><productname>eCos</productname> has been designed to support
applications with real-time requirements, providing features such as
full preemptability, minimal interrupt latencies, and all the
necessary synchronization primitives, scheduling policies, and
interrupt handling mechanisms needed for these type of
applications. <productname>eCos</productname> also provides all the
functionality required for general embedded application support
including device drivers, memory management, exception handling, C,
math libraries, etc. In addition to runtime support, the
<productname>eCos</productname> system includes all the tools
necessary to develop embedded applications, including
<productname>eCos</productname> software configuration and build
tools, and GNU based compilers, assemblers, linkers, debuggers, and
simulators.</PARA>

<PARA>To get the most out of <productname>eCos</productname> you