From 5741c943d00d515de7dd489ca0fd7807903e25d3 Mon Sep 17 00:00:00 2001 From: Joel Sherrill Date: Sat, 11 Apr 1998 14:54:09 +0000 Subject: Added cross development and real-time embedded systems background. --- doc/started/intro.t | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 98 insertions(+) (limited to 'doc/started/intro.t') diff --git a/doc/started/intro.t b/doc/started/intro.t index 96826f1ec6..87e0552aa0 100644 --- a/doc/started/intro.t +++ b/doc/started/intro.t @@ -21,4 +21,102 @@ essentials for performing a setup of the following items: @item GDB Debugger @end itemize +The remainder of this chapter provides background information on real-time +embedded systems and cross development. If you are not familiar with either +of these areas, please read them. This will help familiarize you with the +types of systems RTEMS is designed to be used in and the cross development +process used when developing RTEMS applications. + +@section Real-Time Embedded Systems + +Real-time embedded systems are found in practically every facet of our +everyday lives. Today's systems range from the common telephone, automobile +control systems, and kitchen appliances to complex air traffic control +systems, military weapon systems, an d production line control including +robotics and automation. However, in the current climate of rapidly changing +technology, it is difficult to reach a consensus on the definition of a +real-time embedded system. Hardware costs are continuing to rapidly decline +while at the same time the hardware is increasing in power and functionality. +As a result, embedded systems that were not considered viable two years ago +are suddenly a cost effective solution. In this domain, it is not uncommon +for a single hardware configuration to employ a variety of architectures and +technologies. Therefore, we shall define an embedded system as any computer +system that is built into a larger system consisting of multiple technologies +such as digital and analog electronics, mechanical devices, and sensors. + +Even as hardware platforms become more powerful, most embedded systems are +critically dependent on the real-time software embedded in the systems +themselves. Regardless of how efficiently the hardware operates, the +performance of the embedded real-time software determines the success of the +system. As the complexity of the embedded hardware platform grows, so does +the size and complexity of the embedded software. Software systems must +routinely perform activities which were only dreamed of a short time ago. +These large, complex, real-time embedded applications now commonly contain +one million lines of code or more. + +Real-time embedded systems have a complex set of characteristics that +distinguish them from other software applications. Real-time embedded +systems are driven by and must respond to real world events while adhering to +rigorous requirements imposed by the environment with which they interact. +The correctness of the system depends not only on the results of +computations, but also on the time at which the results are produced. The +most important and complex characteristic of real-time application systems is +that they must receive and respond to a set of external stimuli within rigid +and critical time constraints. + +A single real-time application can be composed of both soft and hard +real-time components. A typical example of a hard real-time system is a +nuclear reactor control system that must not only detect failures, but must +also respond quickly enough to prevent a meltdown. This application also has +soft real-time requirements because it may involve a man-machine interface. +Providing an interactive input to the control system is not as critical as +setting off an alarm to indicate a failure condition. However, th e +interactive system component must respond within an acceptable time limit to +allow the operator to interact efficiently with the control system. + +@section Cross Development + +Today almost all real-time embedded software systems are developed in a +@b{cross development} environment using cross development tools. In the cross +development environment, software development activities are typically +performed on one computer system, the @b{host} system, while the result of the +development effort (produced by the cross tools) is a software system that +executes on the @b{target} platform. The requirements for the target platform are +usually incompatible and quite often in direct conflict with the requirements +for the host. Moreover, the target hardware is often custom designed for a +particular project. This means that the cross development toolset must allow +the developer to customize the tools to address target specific run-time +issues. The toolset must have provisions for board dependent initialization +code, device drivers, and error handling code. + +The host computer is optimized to support the code development cycle with +support for code editors, compilers, and linkers requiring large disk drives, +user development windows, and multiple developer connections. Thus the host +computer is typically a traditional UNIX workstation such as are available +from SUN or Silicon Graphics, or a PC running either a version of MS-Windows +or UNIX. The host system may also be required to execute office productivity +applications to allow the software developer to write documentation, make +presentations, or track the project's progress using a project management +tool. This necessitates that the host computer be general purpose with +resources such as a thirty-two or sixty-four bit processor, large amounts of +RAM, a monitor, mouse, keyboard, hard and floppy disk drives, CD-ROM drive, +and a graphics card. It is likely that the system will be multimedia capable +and have some networking capability. + +Conversely, the target platform generally has limited traditional computer +resources. The hardware is designed for the particular functionality and +requirements of the embedded system and optimized to perform those tasks +effectively. Instead of hard driverss and keyboards, it is composed of +sensors, relays, and stepper motors. The per-unit cost of the target platform +is typically a critical concern. No hardware component is included without +being cost justified. As a result, the processor of the target system is +often from a different processor family than that of the host system and +usually has lower performance. In addition to the processor families +targeted only for use in embedded systems, there are versions of nearly every +general-purpose process or specifically tailored for real-time embedded +systems. For example, many of the processors targeting the embedded market +do not include hardware floating point units, but do include peripherals such +as timers, serial controllers, or network interfaces. + + -- cgit v1.2.3