08-3 8.3 System-level requirements.pptx

第1页：8.3 生词表

第2页：8.3 生词表（续）

第3页：8.3 生词表（续）

第4页：8.3 常用短语

第5页：3系统级的要求为了在市场中保持竞争力

Inordertobe competitive in the marketplace,embedded systems require that the designers take into account the entire system when making design decisions. 8.3系统级的要求为了在市场中保持竞争力，嵌入式系统要求设计者在设计时要考虑到整个系统。

第6页：与其……不如……”

1. End-product utility The utility of the end product is the goal when designing an embedded system,not the capability of the embedded computer itself.[1]Embedded products are typically sold on the basis of capabilities,features,and system cost rather than which CPUisusedin them or cost/performance of that CPU.分析：句中的ratherthan，表示客观事实，意为“是……而不是……；与其……不如……”。它连接的并列成分可以是名词、代词、形容词、介词(短语)、动名词、分句、不定式、动词等。1.最终产品的效用在设计嵌入式系统时，目标是最终产品的效用而不是嵌入式计算机本身的能力。嵌入式产品销售的基础是它们的功能、特点和系统成本，而不是它们所用的CPU或这个CPU的成本/性能。

第7页：8.3 系统级需求 课文要点

Onewayof looking at an embedded system is that the mechanisms and their associated I/Oarelargely defined by the application. Then,software is used to coordinate the mechanisms and define their functionality,often at the level of control system equations or finite state machines. Finally,computer hardware is made available as infrastructure to execute the software and interface it to the external world.[2]Whilethismay not be an exciting way for a hardware engineer to look at things,it does emphasize that the total functionality delivered by the system is what is paramount.分析：句中what is paramount为what引导的名词性从句，在句中作表语｡例如:The president’s meaning is just what we want to express.主席所表达的意思正是我们所要说的｡我们可以认为嵌入式系统的机制及其相关的I/O主要由应用限定。其次，通常在控制系统方程或有限状态机的层次上，用软件协调这些机制并确定其功能。最后，电脑硬件作为基础设施来执行软件的功能，实现软件与外部世界的连接。虽然硬件工程师看待事物的这一方式可能并不新鲜，但它强调指出系统提供的总体功能是至关重要的。

第8页：设计的挑战

设计的挑战：软件和I/O驱动的硬件综合（而不是硬件驱动的软件汇编/综合）。Designchallenge:Software-andI/O-driven hardware synthesis(as opposed to hardware-driven software compilation/synthesis).

第9页：系统安全性和可靠性整个嵌入式系统的安全性

2.Systemsafety&reliability It is the safety and reliability of the total embedded system that really matters. The Distributed system example is mission critical,but does not employ computer redundancy. Instead,mechanical safety backups are activated when the computer system loses control in order to safely shutdown system operation. 2.系统安全性和可靠性整个嵌入式系统的安全性和可靠性确实非常重要。分布式系统例子是关键任务，但不采用计算机冗余。相反，当计算机系统失去控制时，为了安全关闭系统操作，会激活机械安全备份。

第10页：系统级上更大

Abiggerand more difficult issue at the system level is software safety and reliability. While software doesn't normally"break"in the sense of hardware,it maybe so complex that a set of unexpected circumstances can cause software failures leading to unsafe situations. This is a difficult problem that will take many years to address,and may not be properly appreciated by non-computer engineers and managers involved in system design decisions.系统级上更大、更棘手的问题是软件的安全性和可靠性。尽管软件通常不会有硬件意义上的“断裂损坏”，但软件太复杂，有时一系列意外情况可能会导致软件故障而导致不安全。这是一个需要许多年才能解决的难题，参与系统设计决策的非计算机工程师和管理人员可能并没有正确理解这一问题。

第11页：价格低廉的、现有的使用不可靠部件的系统

Design challenges:Reliable software.Cheap, available systems using unreliable components.Electronic vs. non-electronic design tradeoffs.设计的挑战：可靠的软件。价格低廉的、现有的使用不可靠部件的系统。电子与非电子设计权衡

第12页：控制物理系统嵌入计算机的通常原因

3.Controlling physical systems The usual reason for embedding a computer is to interact with the environment,often by monitoring and controlling external machinery. Inordertodo this,analog inputs and outputs must be transformed to and from digital signal levels. Additionally,significant current loads may need to be switched in order to operate motors,lightfixtures,and other actuators. All these requirements can lead to a large computer circuit board dominated by non-digital components. 3.控制物理系统嵌入计算机的通常原因是通过监测和控制外部机械与环境互相作用。为了做到这一点，模拟输入要转换为数字信号输入，而数字信号输出要转换为模拟输出。此外，为了操作电机、灯具和其他驱动器，可能需要放大驱动电流。满足这些要求需要设计一个以非数字部件为主的大型计算机电路板。

第13页：在一些系统中

Insomesystems"smart"sensors and actuators(that contain their own analog interfaces,powerswitches,andsmallCPUS)maybe used to off-load interface hardware from the central embedded computer. This brings the additional advantage of reducing the amount of system wiring and number of connector contacts by employing an embedded network rather than a bundle of analog wires. However,this change brings with it an additional computer design problem of partitioning the computations among distributed computers in the face of an inexpensive network with modest bandwidth capabilities.在一些系统中，“智能”传感器和驱动器（包含自己的模拟接口、电源开关和小CPU）可用于从中心嵌入式计算机中卸下接口硬件。这带来更多的优势：通过采用嵌入式网络而不是一堆模拟信号线，减少了系统的布线和连接器接点。然而，这种变化也带来了计算机设计的其他问题，即面对具有低带宽能力的廉价网络如何在分布式计算机之间分配计算。

第14页：设计的挑战

Designchallenge:Distributed system tradeoffs among analog,power,mechanical,network,and digital hardware plus software.设计的挑战：分布式系统在模拟、电力、机械、网络和数字硬件加软件之间权衡。

第15页：8.3 系统级需求 课文要点

4.Powermanagement[3]A less pervasive system-level issue,but one that is still common,is a need for power management to either minimize heat production or conserve battery power. Whilethepush to laptop computing has produced"low-power"variants of popular CPUs,significantly lower power is needed in order to run from inexpensive batteries for 30 days in some applications,and up to 5 years in others.分析：句中but one that is still common，作A less pervasive system-level issue的同位语。4.电源管理一个不太普遍但仍常见的系统级问题是：电源管理需要最大限度地减少热量产生或节约电池电能。虽然随着便携计算的推出产生了“低功耗”的流行处理器的变体，但仍需要特低功耗以实现由电池供电，包括在某些应用中使用30天的廉价电池、以及在其它应用中使用5年的电池。

第16页：设计的挑战

Design challenge:Ultra-low power design for long-term battery operation.设计的挑战：为长期用电池供电设计超低功耗设备。

第17页：习题8.3 一 判断正误

习题8.3 一 判断正误：根据课文内容判断下列说法正误。

Put“true”or“false”in the brackets for the following statements according to the passage.

1. ()Which CPUisusedin embedded products or the cost/performance of that CPU determines the sale of embedded products.
2. ()The safety and reliability of the total embedded system is of real importance.
3. ()Software normally“breaking”in the sense of hardware is a difficult problem that will take many years to address.
4. ()Employing an embedded network will reduce the amount of system wiring and number of connector contacts.
5. ()Even hardware engineers emphasize the great importance of the total functionality delivered by the embedded system.
6. ()Designers take into account the entire system when making design decisions.
7. ()The utility of the end product is the goal when designing an embedded system, not the capability of the embedded computer itself.
8. ()Embedded products are typically sold on the performance of the CPU.

第18页：习题8.3 二 练习

习题8.3 二 练习：根据课文内容完成下列练习。

Fillinthe blanks according to the passage.

1. Software is used to________the mechanisms and define their functionality, often at the level of control system equations or finite state machines.
2. Abiggerand more difficult issue at the system level is software______and________.
3. The Distributed system example is mission_____, but does not employ computer______.
4. Inordertoem bed a computer, analog inputs and outputs must be transformed to and from_________signal levels.
5. A less pervasive system-level but still common issue is a need for power management to either___________heat production or_________battery power.
6. The usual reason for embedding a computer is_______________.
7. Designers take into account the________when making design decisions.
8. Embedded products are typically sold on the basis of_______, features, and__________.

第19页：习题8.3 三 翻译

习题8.3 三 翻译：将下列单词和短语译成中文。

Translate the following words and expressions into Chinese.

1. end-product utility
2. mechanical safety backups
3. “smart”sensors
4. coordinate
5. take into account
6. computer redundancy
7. analog inputs and outputs
8. computer circuit board
9. infrastructure
10. off-load