当使能的中断事件发生时CPU 会自动去执行对应地址上的内部子程序。句中When an event enabled for interrupts occurs 作为时间状语。
5.4 Instruction and Memory
1. The MCS-48 “MOVP” instruction replacement and all conditional jump instructions operate
relative to the program counter, with the actual jump address computed by the CPU during instruction execution.
MCS-48 “MOVP” 指令的替代和所有条件跳转指令的操作都和程序指针有关，这些指令的实际跳转地址是在指令执行时由CPU 计算得到的。
2. The “MOVP3” and “JMPP” replacements are now made relative to another sixteen-bit register,
which allows the effective destination to be anywhere in the program memory space, regardless of where the instruction itself is located.
“MOVP3” 和 “JMPP” 的替换与另外一个16 位的寄存器有关，该寄存器使得指令不用关心它自己的地址就可以在程序空间的任何有效地址进行寻址。 3. Virtually all instructions execute in either one or two instruction cycles one or two microseconds with a 12MHz crystal with the sole exceptions (multiply and divide) completing in four cycles.
大多数指令执行不是1 个指令周期就是2 个指令周期，如果用12 MHz 的晶体，执行一条指令需要1 或2 微秒的时间，唯一例外的是乘法和除法指令，它们的执行需要四个指令周期。
4. Generalized addressing modes for byte and bit instructions reduce the number of source code lines written and debugged for a given application.
字节和位操作指令的通用寻址模式降低了源代码的长度和调试难度。
5. Since this is the basic width of the ALU and the
different memory types, those resources can be used by the addressing mechanisms, contributing greatly to the computer?s operating efficiency.
这些资源由寻址机构操作（片上数据存储器），它们采用ALU 的基本宽度和不同的存储器类型，这样做有利于提高计算机的运行效率。
5.5 Interfacing AT24CXX Serial
1. Serial memory devices offer significant advantages
over parallel devices in applications where lower data transfer rates are acceptable.
在低速数据传输场合，串行存储器件相对于并行器件具有明显的优势。
2. This application note presents a suite of software routines which may be incorporated into a user?s
application to allow an AT89CX051 microcontroller to read and write AT24CXX serial EEPROMs.
这篇文章讲述了一个AT89CX051 微控制器读写串行EEPROM（AT24CXX）的程序，这段程序可以直接应用到实际系统中去。
3. The clock is generated by the bus master and data is transmitted serially on the data line, most significant bit first, synchronized to the clock.
时钟信号由总线主机产生，数据在数据线上按时钟的节拍串行传输，最高位在前。
4. The fixed portion must match the value hard-wired into the slave, while the programmable portion allows the master to select between a maximum of eight slaves of similar type on the bus.
固定域必须和从机的硬件线路连接相匹配，然而可编程域不同，主机用可编程域来选择总线
上的从机，总线上最多可以有八个类似的从机。 5. A slave which is busy when addressed may not generate an acknowledge.
当寻址从机时，如果该从机正忙，则不会产生应答信号。
句中which is busy when addressed 修饰A slave，when addressed 作为时间状语。
6. If the master has ordered a read operation, it releases the data line and clocks in data sent by the slave.
如果主机决定执行读操作，那么它将释放数据线，同时将从机发送的数据根据时钟移位接收。
5.6 How to Implement More than 64K in 8051
1. Some solutions in the market, including a Philips forum file, refers to split the 64K in two 32K
pages, so the lower 32K still to be always the same as the first 32K of the 512K EPROM.
市场上的一些方案，包括Philip 的正式文件，都是把64K 空间分割成两个32K 页面，这样做意味着
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512K EPROM空间中按64K 划分成大页面，则64K 大页面中的低32K 都是相同的。
2. The same problem resides for the power on, when the port pins goes high after the reset. The solution for that is just use a simple instruction as MOV P1,#00H as the first bytes of every
64K page, so whenever the machine is initialized, independently of what is in those three
addressing lines P1.0, P1.1 and P1.2, the first instruction just drop the selection for the first 64K page, the correct boot page.
在上电的时候存在同样的问题，上电复位时，端口管脚全为高电平。为了解决这个问题，可以应用如下的方案：即在每一个64K 页面的第一个字节放置这条指令“MOV P1,#00H”，这样一来，无论机器在什么时间初始化，无论P1.0, P1.1 和P1.2 这三条地址线上是什么，这
第一条指令都会选择第一个64K 页面，即正确的引导页面。
句中the first instruction just drop the selection for the first 64K page, the correct boot page 为主句；
whenever the machine is initialized 作为时间状语；of what is in those three addressing linesP1.0, P1.1 and P1.2 作为条件状语。
3. To make sure that it would be at that page whenever you jump to 100H, you need to implement a little bit that traffic table, and include the selection of these memory banks by those port pins.
无论你什么时间跳转到100H，为了确保程序在选定页面操作，你需要操作切换表里的相关
位，而且要通过对口线的操作选通对应的存储块。 4. You can implement this in several other ways, but the safer way is just do duplicate the traffic table in every 64K page, exactly the same, starting at the address 0100H.
解决这个问题你有好几个方法，但更安全的办法是在每个64K 页面复制切换表，确保相同， 而且起始地址都是0100H。
5. Remember that when you are running your editor assembler, it can not deal with two different
routines at the same address, it means, you can not make it understand that you have some routine
starting at address 0500H in page 1 and another routine starting at 04F0H in the page zero, both
crossing each other.
要清楚，当你运行汇编器时，汇编器并不会在同一地址安排两个不同的子程序，那也就意味着你没有办法让汇编器明白你有一段程序的起始地址在1 页面的0500H，而另外一段程序的起始地址在0 页面的04F0H。
6. It means that if your machine is running the ROUT2 at 0700H at page 1 and an interrupt happens, you have two choices, duplicate its routine in every page, so you don’t need to worry, or then jump to a special routine in the traffic table, that first saves the contents of P1, so it can return to page 1 after the interrupt routine ends, and then jump to a regular traffic routine.
比如机器正在第一页面ROUT2（0700H）地址运行，这时候一个中断产生了，那么你有两个方法可用：其一，在所有的页面复制中断服务程序，这样一来你就没有什么可担忧的；其二，跳转到切换表中特定的中断程序，在这个程序中它会先保存P1 口的值，这样中断结束时机器返回第一页面，然后跳转到正常的切换流程。
句中It means that you have two choices 为主句；duplicate its routine in every page 和or then jump to a special routine in the traffic table 说明two choices。 7. The only difference is that when returning from the interrupt routine, it needs to first restore the old P1 saved at the interrupt routine first bytes,
different from GENRET routine that always returns to caller in page zero.
从中断程序中返回和从正常程序返回的唯一不同之处就是：中断返回需要恢复保存在中断程序第一字节P1 口的值，而正常返回一般是返回到0 页面的调用者。
5.7 A Digital Thermometer Using the AT89C2051 Microcontroller
1. The system, shown in Figure 5.6, can be used as the basis for developing custom solutions for
networked and stand alone data collection and control equipment.
图5.6 所示系统可以作为开发用户具体方案的一个基础，这些方案可以用在网络设备、独立 的数据采集设备和控制设备中。
2. The overhead incurred performing stack
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manipulations is made up by the library functions that are
all hand coded in a highly optimized assembler.
通常操作会引起堆栈操作，这些堆栈操作由库函数组成，这些库函数全由人工编码而且进行了高级优化。
此处Overhead 为“日常开支”的意思，incur 为“招致、导致”的意思。句中incurred performing stack manipulations 修饰The overhead；that are all hand coded in an highly optimized assembler修饰the library functions。
3. The initialization function InitLcd begins at a more rudimentary nibble oriented level since no
assumption can be made as to the operational status of the LCD at this time.
初始化函数InitLcd 在一个基本的、功能有限的条件下启动，因为此时难以确定LCD 的工作状态。 4. The DS1620 contains all temperature measurement and signal conditioning circuitry on-chip and
presents the processor with a 3-wire digital interface composed of a bi-directional data line DQ, a reset input \\RST, and a clock input CLK.
DS1620 包含有温度测量和信号调整电路，它和微处理器的连接只需要三根数字接口线，其中一根是双向数据线DQ、一根是复位输入线\\RST、还有一根是时钟输入线CLK。句中contains 和presents 并列。 5. Data bits received by the processor are output on the falling edge of the clock and remain validthrough the rising edge.
由处理器接收的数据位在时钟的下降沿被输出，而且在上升沿到来之前一直保持有效。
6. Once in continuous conversion mode, the actual conversion process is started by issuing the start conversion command through TempConvert.
一旦进入连续转换模式，实际转换过程的启动是通过TempConvert 发出启动命令来实现的。
7. Unlike the often impenetrable gyrations that result when working with numbers in assembler, the
C representation of this calculation is perfectly clear in intent and function.
并不像在汇编器中处理数字那样繁琐，这种计算用C 语言表示无论结果还是函数都更为清楚。
6.1 What Is Telecommunication?
1. The telephony infrastructure includes
cross-continental fiber optic cable to facilitate
international voice telecommunications and national and regional cabling to connect long distance calls. 电话的结构包括用于洲际语音通信的光缆和用于长途电话的国家及区域电缆网络。
句中cross-continental fiber optic cable to facilitate international voice telecommunications 和national and regional cabling to connect long distance calls 是并列结构。
2. Newer data telecommunications technology is not only faster, but it also ensures better accuracy due to more reliable transmission media and techniques that enable the receiver to monitor the integrity of the data it has received.
由于采用了更为可靠的传输介质，安装了具有接收数据校验功能的设备，更新的数据通信技术不但更快，而且准确性更高。句中为not only … but also…结构。
3. However, as you might guess, the distinctions between what each of these equipment providers manufactures and what each of the service providers carries are also blurring as voice and video signals are increasingly carried over data connections.
就像声音信号和视频信号逐渐用数据通信来传输一样，制造商生产什么样的设备和服务商提供什么样的服务之间的区别是很模糊的。句中between what each of these equipment providers manufactures and what each of the service providers carries 修饰the distinctions，作为主语。
6.2 Signals
1. One situation in which you are likely to use analog signals to transmit data is when using a modem to connect two systems.
用调制解调器连接计算机是你能用模拟信号传输数据的一种情况。句中 in which you are likely to use analog signals to transmit data 修饰主语One situation。
2. The word modem derives from its function as a modulator/demodulator, modulating analog signals into digital signals at the transmitting end, then demodulating digital signals into analog signals at the receiving end.
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调制解调器这个词来源于它作为调制器和解调器的功能，调制器就是在发送端把数字信号调制成模拟信号；解调器就是在接收端把模拟信号变回数字信号。
句中modulating analog signals into digital signals at the transmitting end 说明modulator；then
demodulating digital signals into analog signals at the receiving end 说明demodulator。
3. For example, the type of transmitter used for radio broadcasts and the way in which this
transmitter manipulates currents to produce signals is different from the transmitter and signaling technique used on a network.
例如：用于无线电广播的发送器和用于网络的发送器是不同的，同样用于前者的发送器转换
电流成为信号的方式和用于后者的发送技术也是不同的。
句中the type of transmitter used for radio broadcasts and the way in which this transmitter
manipulates currents to produce signals 和 the transmitter and signaling technique used on a network 做比较。
6.3 Modulation
1. Uncontrolled electromagnetic energy radiates freely and chaotically in many directions, much like
waves of water in a large pool that contains a number of splashing children.
不受控的电磁能在多个方向上随机地、混乱地辐射，这就像很多小孩子在一个大水塘里随意泼水所形成的混乱的水波一样。
2. Modulation is a technique for processing signals in which two waves are combined to produce a
wave that possesses characteristics of both and can be decoded to separate these characteristics.
调制是一种信号处理技术，处理信号时,将两个波合成一个具有两者特性且能通过解码分离出这些特性的波。
句中 in which two waves are combined to produce a wave that possesses characteristics of both and can be decoded to separate these characteristics 修饰processing signals；该句中的that possesses
characteristics of both and can be decoded to separate these characteristics 修饰a wave。
3. Frequency is the number of times a wave cycles from its beginning point to its highest amplitude, to its lowest amplitude and back to where it started within a given time frame.
频率是一个波形在给定时间内从开始点到最高幅值、再到最低幅值、最后回到开始点的周期个数。
6.4 Communication Systems Components
1. A telecommunication network permits the
transmission of sound, video, computer data or other information between the telephone or other terminal device (such as a computer or facsimile machine) of one party and the telephone or other terminal device of another party by establishing a connection between the telephones or terminal devices of the parties.
通信网络通过建立两个设备之间的连接可以在两个设备之间传输声音、图像、计算机数据或其他信息，通讯可以在电话之间，也可以在像计算机、传真机一类的其他设备之间完成。
句中 the telephone or other terminal device (such as a computer or facsimile machine) of one party 和 the telephone or other terminal device of another party 为between … and …句法；by establishing a connection between the telephones or terminal devices of the parties 为方式状语。
2. A TV program down your phone line, a book you read or play on your computer screen and photos
without film are all signs of a coming together of some of the most important industries of the 1990s.
通过电话线下载电视节目、通过计算机读书以及看不用胶片的照片，这些例子都是20 世纪90 年代一些最主要的产业融合标志。
3. The telephone system has also changed enormously since the 1950s. The transition from analogue transmission of voice over a twisted pair of copper wires to the digital transmission of voice, data
and images through the network has been phenomenal. 20 世纪50 年代以后电话系统已经发生了翻天覆地的变化。原来利用双绞铜线传输模拟语音信号，但今天通过网络传输数字语音信号、数据和图像，这种转变已经是很明显了。
句中The transition 作为主语，from analogue
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transmission of voice over a twisted pair of copper wires to the digital transmission of voice, data and images through the network 修饰The transition，该句为from … to … 结构。
6.5 Public Switched Telephone Network
1. The portion of the PSTN which comprises the transmission system between the telephone and the exchange to which the customer is connected is known as the Customer Access Network (“CAN”).
PSTN 有一部分传输系统用于连接电话和用户端交换，该系统就是众所周知的“用户存取网络”，简称“CAN”。
句中the PSTN which comprises the transmission system between the telephone and the exchange
to which the customer is connected 修饰The portion。2. If, on the other hand, the called party is connected to a different local exchange, then the local
exchange of the calling party connects the calling party either to the local exchange of the called
party or to some other exchange from which further connections can be made which will
ultimately establish a connection between the calling party and the called party.
换句话说，如果被叫方被连接在一个不同的本地交换网络，那么本地主叫网络要么通过本地被叫网络要么通过其他交换方式连接主叫方和被叫方，其他交换方式无论如何最后都要完成主叫方和被叫方的连接。
句中to the local exchange of the called party 和to some other exchange 为either?or?句法，
其中from which further connections can be made which will ultimately establish a connection
between the calling party and the called party 修饰some other exchange。
3. The quality and capacity of radio transmissions depend upon many factors including the power of the radio transmitter and its antenna, and the radio frequency upon which the transmission is to occur.
无线电传输的质量和容量受诸多因素的影响，这些因素有无线电发射器的功率、发射天线的
功率和无线电发射频率。
句中including the power of the radio transmitter and its antenna, and the radio frequency upon
which the transmission is to occur 修饰many factors。 4. If there was no switching system it would be necessary for a party to establish a separate and permanent connection from the party?s telephone to each other telephone to which the party
wanted to make, or from which the party wanted to receive, telephone calls.
假如没有交换系统，那么对于一部电话来说，它必须和计划与它通话的所有电话建立一个分散的永久的连接。
句中it would be necessary for a party to establish 是 “?for sb. to do sth.” 句式；from the
party?s telephone to each other telephone to which the party wanted to make 和 from which the
party wanted to receive, telephone calls 并列。
7.1 What Is an Embedded System
1. As Figure 7.1 indicates, the previous generations include mainframes (one per enterprise), which
were displaced by minicomputers (smaller, but one per department), which in turn were displaced
by personal computers (smaller still, but one per person).
就像图7.1 指明的先前的变革包括巨型机（一个企业一台），后来巨型机被小型机替代（机器比较小，但一个部门一台），就在这个变革的过程中，小型机又被微型机替代（微型机更小，但一人一台）。 2. Many processors are available as “soft cores” described by relatively high-level hardware
descriptive languages so that they can be integrated with some effort into SoC projects.
许多的处理器具有“软核”版本，这些“软核”是用一种高级硬件描述语言来描述的，这样做就是为了能够把这些“软核”处理器综合成“片上系统”产品。
3. Systems that contain a microprocessor largely invisible to the user and systems in which the user is never, or rarely, expected to load a program are examples of embedded systems.
包含对用户基本不可见处理器的系统和不希望用户自己装载程序的系统都是嵌入式系统的例子。
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