外文原文
A: Fundamentals of Single-chip Microcomputer
The single-chip microcomputer is the culmination of both the development of the digital computer and the integrated circuit arguably the tow most significant inventions of the 20th century
These tow types of architecture are found in single-chip microcomputer. Some employ the split program/data memory of the Harvard architecture, shown in Fig.3-5A-1, others follow the philosophy, widely adapted for general-purpose computers and microprocessors, of making no logical distinction between program and data memory as in the Princeton architecture, shown in Fig.3-5A-2.
In general terms a single-chip microcomputer is characterized by the incorporation of all the units of a computer into a single device, as shown in
Fig.3-5A-1 A Harvard type
Read only memory (ROM)
ROM is usually for the permanent, non-volatile storage of an applications program .Many microcomputers and microcontrollers are intended for high-volume applications and hence the economical manufacture of the devices requires that the contents of the program memory be committed permanently during the manufacture of chips . Clearly, this implies a rigorous approach to ROM code development since changes cannot be made after manufacture .This development process may involve emulation using a sophisticated development system with a hardware emulation capability as well as the use of powerful software tools.
Some manufacturers provide additional ROM options by including in their range devices with (or intended for use with) user programmable memory. The simplest of these is usually device which can operate in a microprocessor mode by using some of the input/output lines as an address and data bus for accessing external memory. This type of device can behave functionally as the single chip microcomputer from which it is derived albeit with restricted I/O and a modified external circuit. The use of these ROM less devices is common even in production circuits where the volume does not justify the development costs of custom on-chip ROM[2];there can still be a significant saving in I/O and other chips compared to a conventional microprocessor based circuit. More exact replacement for ROM devices can be obtained in the form of variants with 'piggy-back' EPROM(Erasable programmable ROM )sockets or devices with EPROM instead of ROM 。These devices are naturally more expensive than equivalent ROM device, but do provide complete circuit equivalents. EPROM based devices are also extremely attractive for low-volume applications where they provide the advantages of a single-chip device, in terms of on-chip I/O, etc. ,with the convenience of flexible user programmability.
Random access memory (RAM).
RAM is for the storage of working variables and data used during program execution. The size of this memory varies with device type but it has the same characteristic width (4,8,16 bits etc.) as the processor ,Special function registers, such as stack pointer or timer register are often logically incorporated into the RAM area. It is also common in Hard type microcomputers to treat the RAM area as a collection of register; it is unnecessary to make distinction between RAM and processor register as is done in the case of a microprocessor system since RAM and registers are not usually physically separated in a microcomputer .
Central processing unit (CPU).The CPU is much like that of any microprocessor. Many applications of microcomputers and microcontrollers involve the handling of binary-coded decimal (BCD) data (for numerical displays, for example) ,hence it is common to find that the CPU is well adapted to handling this type of data .It is also common to find good
facilities for testing, setting and resetting individual bits of memory or I/O since many controller applications involve the turning on and off of single output lines or the reading the single line. These lines are readily interfaced to two-state devices such as switches, thermostats, solid-state relays, valves, motor, etc.
Parallel input/output.
Parallel input and output schemes vary somewhat in different microcomputer; in most a mechanism is provided to at least allow some flexibility of choosing which pins are outputs and which are inputs. This may apply to all or some of the ports. Some I/O lines are suitable for direct interfacing to, for example, fluorescent displays, or can provide sufficient current to make interfacing other components straightforward. Some devices allow an I/O port to be configured as a system bus to allow off-chip memory and I/O expansion. This facility is potentially useful as a product range develops, since successive enhancements may become too big for on-chip memory and it is undesirable not to build on the existing software base.
Serial input/output .
Serial communication with terminal devices is common means of providing a link using a small number of lines. This sort of communication can also be exploited for interfacing special function chips or linking several microcomputers together .Both the common asynchronous synchronous communication schemes require protocols that provide framing (start and stop) information .This can be implemented as a hardware facility or U(S) ART(Universal(synchronous) asynchronous receiver/transmitter) relieving the processor (and the applications programmer) of this low-level, time-consuming, detail. t is merely necessary to selected a baud-rate and possibly other options (number of stop bits, parity, etc.) and load (or read from) the serial transmitter (or receiver) buffer. Serialization of the data in the appropriate format is then handled by the hardware circuit.
Timing/counter facilities.
Many application of single-chip microcomputers require accurate evaluation of elapsed real time .This can be determined by careful assessment of the execution time of each branch in a program but this rapidly becomes
inefficient for all but simplest programs .The preferred approach is to use timer circuit that can independently count precise time increments and generate an interrupt after a preset time has elapsed .This type of timer is usually arranged to be reloadable with the required count .The timer then decrements this value producing an interrupt or setting a flag when the counter reaches zero. Better timers then have the ability to automatically reload the initial count value. This relieves the programmer of the
responsibility of reloading the counter and assessing elapsed time before the timer restarted ,which otherwise wound be necessary if continuous precisely timed interrupts were required (as in a clock ,for example).Sometimes
associated with timer is an event counter. With this facility there is usually a special input pin , that can drive the counter directly.
Timing components.
The clock circuitry of most microcomputers requires only simple timing components. If maximum performance is required, a crystal must be used to ensure the maximum clock frequency is approached but not exceeded. Many clock circuits also work with a resistor and capacitor as low-cost timing components or can be driven from an external source. This latter arrangement is useful is external synchronization of the microcomputer is required.
B:PLC[1]
PLCs (programmable logical controller) face ever more complex challenges these days . Where once they quietly replaced relays and gave an occasional report to a corporate mainframe, they are now grouped into cells, given new job and new languages, and are forced to compete against a growing array of control products. For this year's annual PLC technology update ,we queried PLC makers on these topics and more .
Programming languages
Higher level PLC programming languages have been around for some time ,but lately their popularity has mushrooming.
PLCs in process control
Thus far, PLCs have not been used extensively for continuous process control .Will this continue?
Several vendors -obviously betting that the opposite will happen -have introduced PLCs optimized for process application .Rich Ryan, manger, commercial marketing, Allen-bradley Programmable Controls Div., cites PLCs's increasing use such industries as food ,chemicals ,and petroleum. Ryan feels there are two types of applications in which they're appropriate.
controller makes sense for small, low loop count application .The second is where you have to integrate the loop closely with the sequential logical .Batch controllers are prime example ,where the sequence and maintaining the process variable are intertwined so closely that the benefits of having a programmable controller to do the sequential logical outweighs some of the disadvantages of not having a distributed control system.
Bill Barkovitz, president of Triconex, predicts that
Communications and MAP
Communications are vital to an individual automation cell and to be automated factory as a whole. We've heard a lot about MAP in the last few years ,and a lot of companies have jumped on the bandwagon.[2]Many, however, were disappointed when a fully-defined and completed MAP specification didn't appear immediately .Says Larry Komarek:
Because of this, many PLC vendors are holding off on full MAP implementations. Omron, for example, has an ongoing MAP-compatibility program;[3]but Frank Newburn, vice president of Omron's Industrial Division ,reports that because of the lack of a firm definition ,Omron's PLCs don't yet talk to MAP.
Since it's unlikely that an individual PLC would talk to broad MAP anyway, makers are concentrating on proprietary networks. According to Sal Provanzano, users fear that if they do get on board and vendors withdraw from MAP, they'll be the ones left holding a communications structure that's not supported.
Universal I/O
While there are concerns about the lack of compatible communications between PLCs from different vendors, the connection at the other end-the I/O-is even more fragmented .With rare exceptions, I/O is still proprietary .Yet there are those who feel that I/O will eventually become more universal .GE Fanuc is hoping to do that with its Genius smart I/O line. The independent I/O makers are pulling in the same direction.
Many say that I/O is such a high-value item that PLC makers will always want to keep it proprietary .As Ken Jannotta, says:
With more intelligent I/O appearing, Sal Provanzano feels this will lead
to more differentiation among I/O from different makers.
Connecting PLC I/O to PCs
While different PLCs probably will continue to use proprietary I/O, several vendors make it possible to connect5 their I/O to IBM PC-compatible equipment. Alle-bradeley, Could, and Cincinnati Milacron already have, and rumor has it that GE is planning something along these same lines .[4]Bill Ketelhut, manage of product planning at GE Fanuc North America ,sees this sort of thing as alternative to universal I/O.
PLCs VS PCs
If the IBM 7552, the Action Instruments BC22,and other computers are appearing on the factory floor, won't this mean new competition for PLCs? Rich Ryan:
外文资料翻译译文
单片机基础
单片机是电脑和集成电路发展的巅峰，有据可查的是他们也是20世纪最有意义的两大发明。
这两种特性在单片机中得到了充分的体现。一些厂家用这两种特性区分程序内存和数据内存在硬件中的特性，如图3-5A-1，依据同样的原理广泛的适用于一般目的的电脑和微电脑，一些厂家在程序内存和数据内存之间不区分的像Princeton特性，展示如图3-5A-2.
只读存贮器(ROM). ROM是通常的永久性的，非应用程序的易失性存储器。不少微机和单片机用于大批量应用，因此，经济的设备制造要求的程序存储器的内容是在制造期间永久性的刻录在芯片中，这意味着严谨的方法，因为修改ROM代码不能制造之后发展。这一发展过程可能涉及仿真,使用硬件仿真功能以及强大的软件工具使用先进的开发系统。
一些制造商在其提供的设备包括的范围（或拟使用）用户可编程内存.其中最简单的通常是设备能够运行于微处理器模式通过使用一些输入/输出作为地址线额外的ROM选项和数据总线访问外部内存.这种类型的设备可以表现为单芯片微型计算机尽管有限制的I / O和外部修改这些设备的电路.小内存装置的应用是非常普遍的在永久性内存的制造中 [2];但仍然可以在我节省大量成本I/ O和其它芯片相比，传统的基于微处理器电路.更准确的ROM设备更换，可在与'形式变种背驮式'EPROM（可擦除可编程只读存储器）插座或存储器，而不是ROM器件。这些器件自然价格比同等ROM设备贵，但不提供完整的等效电路.EPROM的设备也非常有吸引力对于低容量应用中，他们提供的单芯片器件的优势，在以下方面的板载I / O等，在灵活的用户可编程带来的便利。
随机存取存储器（RAM）。RAM用于变量和工作在程序使用该存储器的执行.随数据存储设备的大小不同类型而有所不同，但具有相同的特征宽度（4,8,16 比特等）作为处理器。特殊功能寄存器，如栈指针或定时器寄存器，往往逻辑纳入内存区域.它也在型微电脑的硬件中做集中内存，它是不必要的区分内存和处理器之间的区别在通常不物理上分开的微机中。
中央处理单元（CPU）。CPU是很象微型电子计算机和微控制器的任何微电脑.许多微电脑和微控制器涉及到二进制编码(十进制处理（BCD）的数据为例）数字显示，因而，常常可以发现该CPU是很适合处理这种类型的数据。对设施良好与否进行的测试，设置和重置单个位的内存或I / O控制器的应用程序，也是常见的因为许多涉及打开和关闭的单输出线或在单线.这些线很容易连接到二进制的设备，如开关，恒温器，固态继电器，阀门，电机等
并行输入/ 输出.并行输入和输出的计划有所不同，在不同的微机，在大多数设立一个机制，至少选择让其中一些引脚输出，一些引脚输如是非常灵活的。这可能适用于所有或端口.有些I / O线直接连接到适当的设备，例如，荧光显示器，也可以提供足够的电流，使接口和其他设备直接相连.一些设备允许一个I / O端口,其他组件将作为系统总线配置为允许片外存储器和I / O扩展。这个设施是潜在有用的一个产品系列的发展，因为连续增强可能成为太上存储器，这是不可取的，不是建立在现有的软
件基础上的。
串行输入/输出。串行通信是指与终端设备的链接使用少量的通讯线.这种通讯也可利用特殊的接口连接功能芯片使几个微型机连在一起。双方共同异步同步通信方案要求的规则提供成帧（启动和停止）的信息。这可以作为一个硬件设施或U（拧）艺术（通用执行（同步）异步接收器/发送器）减轻处理器（和应用程序）的这种低层次的确费时.它也只需要选择一个波特率及其他可能的选择（停止位，奇偶校验等）和负载号码（或读取），串行发送器（或接收）的缓冲器.进行适当的格式的数据串行处理，然后由硬件电路完成。
定时/计数器设施。许多应用的单片机需要对过去的真实时间准确的评价。这可以由每个程序中的执行时间分支认真评估，但除最简单的程序外，他的工作效率不高。首选方法是使用计时器电路，能独立计算精确的时间增量，并生成一个预设的时间后中断的时间。这种类型的定时器通常在所要求的数量可重载中应用。计时器然后减少此值产生中断或设置标记时，计数器到达零.更好的计时器有自动加载初始值的功能。这将缓解重新加载计数器和评估所用的时间，计时器重新启动之前这是必要的。有时候与定时器相关的是一个事件计数器。这个设备通常有一个特殊的输入引脚，可直接驱动计数器。
定时元件。大多数微型计算机时钟电路只需要简单的计时元件.如果要求最高性能，必须使用晶体以确保最大时钟频率接近，但不会超出。许多时钟电路，还具有电阻和低电容工作成本定时元件，也可以从外部源驱动。这后一种安排是有用的在微机外部同步是必需的时候。
B:PLC[1]
今天的PLC（可编程逻辑控制器）将面对日益复杂的挑战。一旦他们悄悄地取代继电器，偶尔向主机报告，如果他们将他们比作细胞，赋予新的工作和新的语言，将被迫和大量的控制产品竞争。对于今年的年度PLC技术的更新，我们对PLC的制造商会就这些主题提出更多问题.
编程语言
更高水平的PLC编程语言已经推行有一段时间了，但最近的流行，如雨后春笋般。正如雷蒙德莱韦耶，副总裁兼总经理，西门子能源和自动化公司，可编程控制正在为更复杂的操作使用，梯形逻辑比语言变得更加实际，有效和强大的。举例来说，很难写三角函数使用梯形逻辑。“语言为人们所接受，包括布尔，控制系统流程图，这种功能图及其变化图表语言。而且有越来越多像C和BASIC语言的兴趣。”
在过程的PLC控制
到目前为止，PLC的没有大量用于连续过程控制，会继续吗？“我感觉到了，PLC将用于过程工业，但不一定过程控制。” Jannotta说。 几个供应商，显然是把赌注押在相反会发生，已经实行了PLC的应用优化的过程。富瑞安的经理认为PLC将越来越多地使用食品等行业，化工，石化.Ryan认为有两种类型的应用程序中，他们是合适的。“之一，”他说，“是其中的过程控制系统，目前已被没有理由自动化DCS的大小[分布式控制系统]随着价格标签开始。产品的选择是比较高，可编程控制器为小，低环数的应用意义。第二种是你必须融入顺序逻辑。批次控制循环密切合
作是最好的例子，那里的顺序和维持过程变量是交织在一起的密切合作，使拥有一个可编程控制器的逻辑顺序做的好处远远超过了不具有分布式控制系统的一些缺点。”
Bill Barkovitz， Triconex的总统，预言：“今后所有的控制器在过程控制系统的业务将引用更多的PLC技术， PLC功能比以往任何时候都要多。”
通信和规范
在整体上通信是至关重要的个人自动化单元对自动化工厂来说。我们听说了很多规范在过去数年，许多公司都纷纷跟进。[2]但是，不少人失望的发现完成地图规范并没有立即出现。拉里科马雷克说：“现在，规范仍然是一个移动目标，规范没有最终决定，对于制造商。目前，正在推出的产品样本.人们使其产品满足MAP2.1标准。然而，新标准MAP3.0被引进时，MAP2.1为基础的产品将被淘汰时。”
正因为如此，许多PLC厂商正在制定完整的规范. 例如Omron，拥有一个完整的兼容程序; [3]，但弗兰克纽伯恩，副欧姆龙工业部总裁，报告说，由于缺乏公司的定义，欧姆龙的PLC还谈不上规范。
由于不太可能将个人的PLC广泛的交谈，制造商更专注于专有的网络.按照萨尔Provanzano说法，用户担心，如果他们不从规则上和供应商妥协，他们将要加大对通信结构的不支持。
通用的I / O
然而大多数PLC的兼容问题不同厂商的沟通不够，在另一端连接的I / O问题，更是支离破碎的。除了少数例外，I / O是仍然专有技术。然而，谁是那些感觉的I / O最终将成为更具有普遍性。GE Fanuc的希望这样做与天才智能I / O线.各个独立I / O制造商都在同一方向进发。
许多人说，I / O是这样一个高价值项目， PLC制造商将永远希望保持它的专有性。由于肯Jannotta。说：“ I / O将在硬件销售中不成比例。当然每个PLC供应商将试图保护这一点。”出于这个原因，他说，PLC的制造商将不会开始销售通用I / O和其他厂商的系统。“如果我们开始销售该产品的实物，那我们还有什么可生产的？”
Jannotta说道
随着更多智能I / O出现，萨尔Provanzano认为在不同的制造商中间这将导致更多的分化。“哪里的I / O变得非常聪明，并成为系统的一部分真的很难定义，哪些是I / O，哪些是CPU.随着分布式的发展，如果你愿意，CPU也同样可以纳入作为I / O的系统”
PLC的 I / O和个人电脑的连接
虽然不同的PLC厂商可能会继续用专有的I / O，但一些厂商使I / O连接到IBM PC这样的兼容设备成为可能.Alle - bradeley和辛辛那提米拉克龙公司已经拥有，并有传言说，通用的电气计划将沿着同样的思路。克特尔胡特， GE Fanuc北美的产品规划经理，认为是I/ O的普及“我想多个主机接口将代替I/O的趋势，”他说。朱迪格洛尔，市场经理，Square
D Automation Products，将PLC看做是工业电脑。
PLC VS电脑
如果IBM 7552，行动仪器BC22，和其他计算机出现在工厂，这意味着不会对PLC的新的竞争？富瑞安：“有一些控制功能，可用于电脑.可编程程序控制器更好的工作已被迫适应这些应用。“然而，在我们调查的厂商多数不认为“个人电脑入侵”将对他们产生问题。大多表示PLC和PC结构上的差别决定他们不同的作用，PC将主管通讯和管理，PLC则进行控制，他们相信这只是意味着，PLC和个人电脑将能够共享相同的数据。
富瑞恩说：“通用的计算机内在结构不同，可编程控制器硬件结构有内置到几乎每一个制造商的可编程控制器。今天定制的硬件来运行梯形逻辑，解决机器代码。”在根本的区别上，他引用了一个称呼“机器状态”。富瑞安说：“当你关闭机器，或中断周期，或者跳转到另一个周期，现场可编程控制器本身记得机器的状态：定时器状态是什么，计
么，锁存的状态是什么,但计算机本身不这样做。” 数器状态是什
外文原文
A: Fundamentals of Single-chip Microcomputer
The single-chip microcomputer is the culmination of both the development of the digital computer and the integrated circuit arguably the tow most significant inventions of the 20th century
These tow types of architecture are found in single-chip microcomputer. Some employ the split program/data memory of the Harvard architecture, shown in Fig.3-5A-1, others follow the philosophy, widely adapted for general-purpose computers and microprocessors, of making no logical distinction between program and data memory as in the Princeton architecture, shown in Fig.3-5A-2.
In general terms a single-chip microcomputer is characterized by the incorporation of all the units of a computer into a single device, as shown in
Fig.3-5A-1 A Harvard type
Read only memory (ROM)
ROM is usually for the permanent, non-volatile storage of an applications program .Many microcomputers and microcontrollers are intended for high-volume applications and hence the economical manufacture of the devices requires that the contents of the program memory be committed permanently during the manufacture of chips . Clearly, this implies a rigorous approach to ROM code development since changes cannot be made after manufacture .This development process may involve emulation using a sophisticated development system with a hardware emulation capability as well as the use of powerful software tools.
Some manufacturers provide additional ROM options by including in their range devices with (or intended for use with) user programmable memory. The simplest of these is usually device which can operate in a microprocessor mode by using some of the input/output lines as an address and data bus for accessing external memory. This type of device can behave functionally as the single chip microcomputer from which it is derived albeit with restricted I/O and a modified external circuit. The use of these ROM less devices is common even in production circuits where the volume does not justify the development costs of custom on-chip ROM[2];there can still be a significant saving in I/O and other chips compared to a conventional microprocessor based circuit. More exact replacement for ROM devices can be obtained in the form of variants with 'piggy-back' EPROM(Erasable programmable ROM )sockets or devices with EPROM instead of ROM 。These devices are naturally more expensive than equivalent ROM device, but do provide complete circuit equivalents. EPROM based devices are also extremely attractive for low-volume applications where they provide the advantages of a single-chip device, in terms of on-chip I/O, etc. ,with the convenience of flexible user programmability.
Random access memory (RAM).
RAM is for the storage of working variables and data used during program execution. The size of this memory varies with device type but it has the same characteristic width (4,8,16 bits etc.) as the processor ,Special function registers, such as stack pointer or timer register are often logically incorporated into the RAM area. It is also common in Hard type microcomputers to treat the RAM area as a collection of register; it is unnecessary to make distinction between RAM and processor register as is done in the case of a microprocessor system since RAM and registers are not usually physically separated in a microcomputer .
Central processing unit (CPU).The CPU is much like that of any microprocessor. Many applications of microcomputers and microcontrollers involve the handling of binary-coded decimal (BCD) data (for numerical displays, for example) ,hence it is common to find that the CPU is well adapted to handling this type of data .It is also common to find good
facilities for testing, setting and resetting individual bits of memory or I/O since many controller applications involve the turning on and off of single output lines or the reading the single line. These lines are readily interfaced to two-state devices such as switches, thermostats, solid-state relays, valves, motor, etc.
Parallel input/output.
Parallel input and output schemes vary somewhat in different microcomputer; in most a mechanism is provided to at least allow some flexibility of choosing which pins are outputs and which are inputs. This may apply to all or some of the ports. Some I/O lines are suitable for direct interfacing to, for example, fluorescent displays, or can provide sufficient current to make interfacing other components straightforward. Some devices allow an I/O port to be configured as a system bus to allow off-chip memory and I/O expansion. This facility is potentially useful as a product range develops, since successive enhancements may become too big for on-chip memory and it is undesirable not to build on the existing software base.
Serial input/output .
Serial communication with terminal devices is common means of providing a link using a small number of lines. This sort of communication can also be exploited for interfacing special function chips or linking several microcomputers together .Both the common asynchronous synchronous communication schemes require protocols that provide framing (start and stop) information .This can be implemented as a hardware facility or U(S) ART(Universal(synchronous) asynchronous receiver/transmitter) relieving the processor (and the applications programmer) of this low-level, time-consuming, detail. t is merely necessary to selected a baud-rate and possibly other options (number of stop bits, parity, etc.) and load (or read from) the serial transmitter (or receiver) buffer. Serialization of the data in the appropriate format is then handled by the hardware circuit.
Timing/counter facilities.
Many application of single-chip microcomputers require accurate evaluation of elapsed real time .This can be determined by careful assessment of the execution time of each branch in a program but this rapidly becomes
inefficient for all but simplest programs .The preferred approach is to use timer circuit that can independently count precise time increments and generate an interrupt after a preset time has elapsed .This type of timer is usually arranged to be reloadable with the required count .The timer then decrements this value producing an interrupt or setting a flag when the counter reaches zero. Better timers then have the ability to automatically reload the initial count value. This relieves the programmer of the
responsibility of reloading the counter and assessing elapsed time before the timer restarted ,which otherwise wound be necessary if continuous precisely timed interrupts were required (as in a clock ,for example).Sometimes
associated with timer is an event counter. With this facility there is usually a special input pin , that can drive the counter directly.
Timing components.
The clock circuitry of most microcomputers requires only simple timing components. If maximum performance is required, a crystal must be used to ensure the maximum clock frequency is approached but not exceeded. Many clock circuits also work with a resistor and capacitor as low-cost timing components or can be driven from an external source. This latter arrangement is useful is external synchronization of the microcomputer is required.
B:PLC[1]
PLCs (programmable logical controller) face ever more complex challenges these days . Where once they quietly replaced relays and gave an occasional report to a corporate mainframe, they are now grouped into cells, given new job and new languages, and are forced to compete against a growing array of control products. For this year's annual PLC technology update ,we queried PLC makers on these topics and more .
Programming languages
Higher level PLC programming languages have been around for some time ,but lately their popularity has mushrooming.
PLCs in process control
Thus far, PLCs have not been used extensively for continuous process control .Will this continue?
Several vendors -obviously betting that the opposite will happen -have introduced PLCs optimized for process application .Rich Ryan, manger, commercial marketing, Allen-bradley Programmable Controls Div., cites PLCs's increasing use such industries as food ,chemicals ,and petroleum. Ryan feels there are two types of applications in which they're appropriate.
controller makes sense for small, low loop count application .The second is where you have to integrate the loop closely with the sequential logical .Batch controllers are prime example ,where the sequence and maintaining the process variable are intertwined so closely that the benefits of having a programmable controller to do the sequential logical outweighs some of the disadvantages of not having a distributed control system.
Bill Barkovitz, president of Triconex, predicts that
Communications and MAP
Communications are vital to an individual automation cell and to be automated factory as a whole. We've heard a lot about MAP in the last few years ,and a lot of companies have jumped on the bandwagon.[2]Many, however, were disappointed when a fully-defined and completed MAP specification didn't appear immediately .Says Larry Komarek:
Because of this, many PLC vendors are holding off on full MAP implementations. Omron, for example, has an ongoing MAP-compatibility program;[3]but Frank Newburn, vice president of Omron's Industrial Division ,reports that because of the lack of a firm definition ,Omron's PLCs don't yet talk to MAP.
Since it's unlikely that an individual PLC would talk to broad MAP anyway, makers are concentrating on proprietary networks. According to Sal Provanzano, users fear that if they do get on board and vendors withdraw from MAP, they'll be the ones left holding a communications structure that's not supported.
Universal I/O
While there are concerns about the lack of compatible communications between PLCs from different vendors, the connection at the other end-the I/O-is even more fragmented .With rare exceptions, I/O is still proprietary .Yet there are those who feel that I/O will eventually become more universal .GE Fanuc is hoping to do that with its Genius smart I/O line. The independent I/O makers are pulling in the same direction.
Many say that I/O is such a high-value item that PLC makers will always want to keep it proprietary .As Ken Jannotta, says:
With more intelligent I/O appearing, Sal Provanzano feels this will lead
to more differentiation among I/O from different makers.
Connecting PLC I/O to PCs
While different PLCs probably will continue to use proprietary I/O, several vendors make it possible to connect5 their I/O to IBM PC-compatible equipment. Alle-bradeley, Could, and Cincinnati Milacron already have, and rumor has it that GE is planning something along these same lines .[4]Bill Ketelhut, manage of product planning at GE Fanuc North America ,sees this sort of thing as alternative to universal I/O.
PLCs VS PCs
If the IBM 7552, the Action Instruments BC22,and other computers are appearing on the factory floor, won't this mean new competition for PLCs? Rich Ryan:
外文资料翻译译文
单片机基础
单片机是电脑和集成电路发展的巅峰，有据可查的是他们也是20世纪最有意义的两大发明。
这两种特性在单片机中得到了充分的体现。一些厂家用这两种特性区分程序内存和数据内存在硬件中的特性，如图3-5A-1，依据同样的原理广泛的适用于一般目的的电脑和微电脑，一些厂家在程序内存和数据内存之间不区分的像Princeton特性，展示如图3-5A-2.
只读存贮器(ROM). ROM是通常的永久性的，非应用程序的易失性存储器。不少微机和单片机用于大批量应用，因此，经济的设备制造要求的程序存储器的内容是在制造期间永久性的刻录在芯片中，这意味着严谨的方法，因为修改ROM代码不能制造之后发展。这一发展过程可能涉及仿真,使用硬件仿真功能以及强大的软件工具使用先进的开发系统。
一些制造商在其提供的设备包括的范围（或拟使用）用户可编程内存.其中最简单的通常是设备能够运行于微处理器模式通过使用一些输入/输出作为地址线额外的ROM选项和数据总线访问外部内存.这种类型的设备可以表现为单芯片微型计算机尽管有限制的I / O和外部修改这些设备的电路.小内存装置的应用是非常普遍的在永久性内存的制造中 [2];但仍然可以在我节省大量成本I/ O和其它芯片相比，传统的基于微处理器电路.更准确的ROM设备更换，可在与'形式变种背驮式'EPROM（可擦除可编程只读存储器）插座或存储器，而不是ROM器件。这些器件自然价格比同等ROM设备贵，但不提供完整的等效电路.EPROM的设备也非常有吸引力对于低容量应用中，他们提供的单芯片器件的优势，在以下方面的板载I / O等，在灵活的用户可编程带来的便利。
随机存取存储器（RAM）。RAM用于变量和工作在程序使用该存储器的执行.随数据存储设备的大小不同类型而有所不同，但具有相同的特征宽度（4,8,16 比特等）作为处理器。特殊功能寄存器，如栈指针或定时器寄存器，往往逻辑纳入内存区域.它也在型微电脑的硬件中做集中内存，它是不必要的区分内存和处理器之间的区别在通常不物理上分开的微机中。
中央处理单元（CPU）。CPU是很象微型电子计算机和微控制器的任何微电脑.许多微电脑和微控制器涉及到二进制编码(十进制处理（BCD）的数据为例）数字显示，因而，常常可以发现该CPU是很适合处理这种类型的数据。对设施良好与否进行的测试，设置和重置单个位的内存或I / O控制器的应用程序，也是常见的因为许多涉及打开和关闭的单输出线或在单线.这些线很容易连接到二进制的设备，如开关，恒温器，固态继电器，阀门，电机等
并行输入/ 输出.并行输入和输出的计划有所不同，在不同的微机，在大多数设立一个机制，至少选择让其中一些引脚输出，一些引脚输如是非常灵活的。这可能适用于所有或端口.有些I / O线直接连接到适当的设备，例如，荧光显示器，也可以提供足够的电流，使接口和其他设备直接相连.一些设备允许一个I / O端口,其他组件将作为系统总线配置为允许片外存储器和I / O扩展。这个设施是潜在有用的一个产品系列的发展，因为连续增强可能成为太上存储器，这是不可取的，不是建立在现有的软
件基础上的。
串行输入/输出。串行通信是指与终端设备的链接使用少量的通讯线.这种通讯也可利用特殊的接口连接功能芯片使几个微型机连在一起。双方共同异步同步通信方案要求的规则提供成帧（启动和停止）的信息。这可以作为一个硬件设施或U（拧）艺术（通用执行（同步）异步接收器/发送器）减轻处理器（和应用程序）的这种低层次的确费时.它也只需要选择一个波特率及其他可能的选择（停止位，奇偶校验等）和负载号码（或读取），串行发送器（或接收）的缓冲器.进行适当的格式的数据串行处理，然后由硬件电路完成。
定时/计数器设施。许多应用的单片机需要对过去的真实时间准确的评价。这可以由每个程序中的执行时间分支认真评估，但除最简单的程序外，他的工作效率不高。首选方法是使用计时器电路，能独立计算精确的时间增量，并生成一个预设的时间后中断的时间。这种类型的定时器通常在所要求的数量可重载中应用。计时器然后减少此值产生中断或设置标记时，计数器到达零.更好的计时器有自动加载初始值的功能。这将缓解重新加载计数器和评估所用的时间，计时器重新启动之前这是必要的。有时候与定时器相关的是一个事件计数器。这个设备通常有一个特殊的输入引脚，可直接驱动计数器。
定时元件。大多数微型计算机时钟电路只需要简单的计时元件.如果要求最高性能，必须使用晶体以确保最大时钟频率接近，但不会超出。许多时钟电路，还具有电阻和低电容工作成本定时元件，也可以从外部源驱动。这后一种安排是有用的在微机外部同步是必需的时候。
B:PLC[1]
今天的PLC（可编程逻辑控制器）将面对日益复杂的挑战。一旦他们悄悄地取代继电器，偶尔向主机报告，如果他们将他们比作细胞，赋予新的工作和新的语言，将被迫和大量的控制产品竞争。对于今年的年度PLC技术的更新，我们对PLC的制造商会就这些主题提出更多问题.
编程语言
更高水平的PLC编程语言已经推行有一段时间了，但最近的流行，如雨后春笋般。正如雷蒙德莱韦耶，副总裁兼总经理，西门子能源和自动化公司，可编程控制正在为更复杂的操作使用，梯形逻辑比语言变得更加实际，有效和强大的。举例来说，很难写三角函数使用梯形逻辑。“语言为人们所接受，包括布尔，控制系统流程图，这种功能图及其变化图表语言。而且有越来越多像C和BASIC语言的兴趣。”
在过程的PLC控制
到目前为止，PLC的没有大量用于连续过程控制，会继续吗？“我感觉到了，PLC将用于过程工业，但不一定过程控制。” Jannotta说。 几个供应商，显然是把赌注押在相反会发生，已经实行了PLC的应用优化的过程。富瑞安的经理认为PLC将越来越多地使用食品等行业，化工，石化.Ryan认为有两种类型的应用程序中，他们是合适的。“之一，”他说，“是其中的过程控制系统，目前已被没有理由自动化DCS的大小[分布式控制系统]随着价格标签开始。产品的选择是比较高，可编程控制器为小，低环数的应用意义。第二种是你必须融入顺序逻辑。批次控制循环密切合
作是最好的例子，那里的顺序和维持过程变量是交织在一起的密切合作，使拥有一个可编程控制器的逻辑顺序做的好处远远超过了不具有分布式控制系统的一些缺点。”
Bill Barkovitz， Triconex的总统，预言：“今后所有的控制器在过程控制系统的业务将引用更多的PLC技术， PLC功能比以往任何时候都要多。”
通信和规范
在整体上通信是至关重要的个人自动化单元对自动化工厂来说。我们听说了很多规范在过去数年，许多公司都纷纷跟进。[2]但是，不少人失望的发现完成地图规范并没有立即出现。拉里科马雷克说：“现在，规范仍然是一个移动目标，规范没有最终决定，对于制造商。目前，正在推出的产品样本.人们使其产品满足MAP2.1标准。然而，新标准MAP3.0被引进时，MAP2.1为基础的产品将被淘汰时。”
正因为如此，许多PLC厂商正在制定完整的规范. 例如Omron，拥有一个完整的兼容程序; [3]，但弗兰克纽伯恩，副欧姆龙工业部总裁，报告说，由于缺乏公司的定义，欧姆龙的PLC还谈不上规范。
由于不太可能将个人的PLC广泛的交谈，制造商更专注于专有的网络.按照萨尔Provanzano说法，用户担心，如果他们不从规则上和供应商妥协，他们将要加大对通信结构的不支持。
通用的I / O
然而大多数PLC的兼容问题不同厂商的沟通不够，在另一端连接的I / O问题，更是支离破碎的。除了少数例外，I / O是仍然专有技术。然而，谁是那些感觉的I / O最终将成为更具有普遍性。GE Fanuc的希望这样做与天才智能I / O线.各个独立I / O制造商都在同一方向进发。
许多人说，I / O是这样一个高价值项目， PLC制造商将永远希望保持它的专有性。由于肯Jannotta。说：“ I / O将在硬件销售中不成比例。当然每个PLC供应商将试图保护这一点。”出于这个原因，他说，PLC的制造商将不会开始销售通用I / O和其他厂商的系统。“如果我们开始销售该产品的实物，那我们还有什么可生产的？”
Jannotta说道
随着更多智能I / O出现，萨尔Provanzano认为在不同的制造商中间这将导致更多的分化。“哪里的I / O变得非常聪明，并成为系统的一部分真的很难定义，哪些是I / O，哪些是CPU.随着分布式的发展，如果你愿意，CPU也同样可以纳入作为I / O的系统”
PLC的 I / O和个人电脑的连接
虽然不同的PLC厂商可能会继续用专有的I / O，但一些厂商使I / O连接到IBM PC这样的兼容设备成为可能.Alle - bradeley和辛辛那提米拉克龙公司已经拥有，并有传言说，通用的电气计划将沿着同样的思路。克特尔胡特， GE Fanuc北美的产品规划经理，认为是I/ O的普及“我想多个主机接口将代替I/O的趋势，”他说。朱迪格洛尔，市场经理，Square
D Automation Products，将PLC看做是工业电脑。
PLC VS电脑
如果IBM 7552，行动仪器BC22，和其他计算机出现在工厂，这意味着不会对PLC的新的竞争？富瑞安：“有一些控制功能，可用于电脑.可编程程序控制器更好的工作已被迫适应这些应用。“然而，在我们调查的厂商多数不认为“个人电脑入侵”将对他们产生问题。大多表示PLC和PC结构上的差别决定他们不同的作用，PC将主管通讯和管理，PLC则进行控制，他们相信这只是意味着，PLC和个人电脑将能够共享相同的数据。
富瑞恩说：“通用的计算机内在结构不同，可编程控制器硬件结构有内置到几乎每一个制造商的可编程控制器。今天定制的硬件来运行梯形逻辑，解决机器代码。”在根本的区别上，他引用了一个称呼“机器状态”。富瑞安说：“当你关闭机器，或中断周期，或者跳转到另一个周期，现场可编程控制器本身记得机器的状态：定时器状态是什么，计
么，锁存的状态是什么,但计算机本身不这样做。” 数器状态是什