中文翻译
可编程控制器
从一个简单的遗产,这显著的系统已经进化到不仅取代机电设备,而是为了解决日益增加的一系列控制问题在这两种过程和非过程控制行业。通过所有的适应情况,这些微处理器将继续作用到动力的新局面,20世纪90年代的自动化的工厂。
历史
在20世纪60年代,机电设备的议事日程的屁股远为控制问题越来越受到关注。这些设备,俗称继电器、正被利用着成千上万的制造过程和控制多个电机和永动机。许多这些继电器被应用在交通行业,更确切的说,汽车工业。这些继电器使用他们数以百计的电线和连接到调用控制解决方案。接力的性能基本可靠——至少是一个单一的装置。但是共同申请继电器板呼吁300 - 500或更多的继电器、可靠性及维护和支持这些电池板相关的问题变得非常巨大的挑战。成本成为了另一个问题,尽管的低成本的圣火传递本身,面板安装成本可能会相当高。总成本包括采购部件、配线和安装的劳动力,可以范围从$ 30 ~ 50美元的传递。更糟的是,不断转变的需要,这个过程称为为复发性修改中的一个控制面板。用继电器,这是一个昂贵的前景所完成的,因为它是一个主要的电路重组的努力,在面板。除了这些改变是有时差,导致second-shift记录维护噩梦月之后。由此可知,这不是希有报废整个控制面板赞成一种新的以适当的部件装上了一个方式适合于新工艺。如果再加上不可预知的,潜在的高成本、维持这些系统在大批量汽车生产线,显然,是有什么东西需要,提高了控制的过程——使它更可靠、更容易解决,并更加适应变化控制的需要。
这东西,在60年代末期,是第一个可编程控制器。这第一次的革命的系统广域网路发展为一
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个特定的反应的需要大汽车制造商在美国。这些早期的控制器,或可编程逻辑控制器(PLC)为代表的第一个系统,1可以用在我的工厂里,2个可能有“逻辑电路重组的改变或组件没有广泛的变化,并对3例诊断和修理时容易出现的问题。
有趣的是,要观察的进展,已经在过去的15年的可编程控制器的区域。先锋国际的60年代后期的产品一定是令人困惑的和令人恐惧的很多的人。例如,发生了什么事,多样和机电设备维修人员被用来修复手工具吗?他们被替换的计算机的伪装成电子设计来取代继电器。即使是编程工具被设计来出现,因为传递等价的报告。现在我们有机会来检查我们的承诺,现在回想起来,那可编程控制器带到制造。
所有的可编程控制器构成的基本功能块。我们将审查每个街区去理解这个关系到控制系统。先看看我们的中心,因为它是心(或至少是大脑)系统。它由一个微处理器、逻辑记忆存放的实际控制逻辑、储存或变量的内存使用数据通常改变为一个函数权为处理器和记忆。接下来的I / O接区。这个函数采取控制水平信号的CPU和将他们转换成电压和电流,适用于连接级别与工厂级传感器和执行器的自诊断。I / O型的范围可以从数字(离散型或开/关),模拟(连续变量),或者其他各种特殊用途的聪明的I / O专门某个特定应用的任务。这里展示的是程序员的,但是它通常只用于最初配置和程序是一个系统,而不需要系统的操作。它也被用于故障诊断系统,并不能证明是一种宝贵的工具,在查明问题的确切原因仍在调查中。这里展示的现场设备代表各种传感器和执行器连接到I / O。这些是胳膊、腿、眼睛、耳朵的系统,包括按钮、限位开关,接近开关,光敏器件、热电偶、取得、位置传感装置,条形码阅读器作为神经网络的输入,导向灯,显示设备,电机起动器、直流和交流驱动、电磁阀、打印机作为输出。
没有一种单一的尝试可能包括它的快速变化的范围,但三个基本特征可以查看给分类工业控制装置作为一个可编程控制器。
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(1)其基本的内部经营是解决逻辑从一开始的记忆体的一些特殊点,如内存或年底结束程序。一旦最终达成共识,操作将再一次开始之初的记忆。该扫描过程一直持续时间从电力供应到它它移开。
(2)编程逻辑是一种传递梯形图。常开,常闭触点和继电器线圈是范围内使用的格式,利用左和右垂直轨道。功率流(象征性的正电子流)是用来确定哪些卷或输出或断开或继续运作。
(3)这台机器是专为工业环境从其基本概念,这种保护是没有添加在稍后的日期。工业环境包括不可靠的交流电源、高温(0到60摄氏度),极端的湿度、振动、射频噪声和其他类似的参数。
通用的应用领域
可编程控制器是用于广泛的控制应用程序的今天,其中许多是在经济上不可能仅仅几年前。这是真正的两个基本原因:1有成本效益,是成本为每I / O点)有明显的改进与价格下跌的微处理器及相关部件的能力,和2控制器,以解决复杂的计算和通信任务使得人们有可能使用它在一台专用电脑以前使用。
应用可编程控制器可分为好几种不同的方式来进行,包括一般及工业应用的类别。但重要的是要理解这个框架,控制器是目前理解和使用,以便充分发挥的现状和未来演变可以审查。它是通过对发电厂的应用程序控制器中可以看到他们的全部的光。在工业领域中的应用包括许多在这两种离散型制造和机械加工等。汽车工业的应用,可编程控制器的起源,不断为客户提供最大的基地的机会的。其他产业的发展,诸如食品加工和公用事业,提供当前的发展机会。
有五种通用的应用领域中,可编程控制器的使用。一个典型的安装将会使用一个或更多的这些综合控制系统的问题。五个地区被解释一般简要如下。
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描述
是一种低功耗、AT89C51单片机为核心的微机与高性能CMOS 8位字节的闪光可编程和次方可擦写只读存储器(PEROM)。该装置采用Atmel制造高密度的非挥发性记忆体的技术并兼容行业标准的引出线通过MCS—51汇编语言指令集。闪光的汉字,允许程序内存被编程in-system或由传统的非易失性存储器存储程序员。结合一个多才多艺的8位单片机上CPU的Flash芯片、Atmel是一个功能强大的单片机AT89C51单片机为核心,提供了一个解决方案highly-flexible许多嵌入式控制应用。
功能特点
提供以下标准的AT89C51单片机的特点:次方字节的闪光,128字节的内存,32岁I / O线,两个16位定时器/计数器,五向量二级中断体系结构,在全双工串行端口,样品的振荡器和时钟电路。此外,AT89C51与静态逻辑设计和操作减少到零频率支持两种软件可节电模式。停止CPU空闲模式的同时让那只公羊来、定时器/计数器、串行端口和中断系统继续运行。Power-down节省RAM模式的内容但冻结该振荡器取消另外的芯片功能直到下一个硬件复位。
销描述
VCC:电压。
地上:地面。
端口0：
端口0是一个8位高电平双向I / O端口。作为一个输出端口,每个插脚陷八TTL的投入。
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当1是写给端口0销,高片选指针可作为输入。端口0也可以被组态的多路复用低片选地址/数据总线访问期间的外部程序和数据的记忆。在这种模式下并有内部变革。端口0,也带走了Flash编程代码字节,并输出期间在program verification代码字节。在program verification外部变化被要求。
端口1：
端口1是一个8位双向I / O端口与内部变化。端口1输出缓冲能沉/源四TTL的投入。当1是写端口1针将内部变化高,可作为输入。为输入变量, 端口1指针,将外部所牵引电流源(IIL)因内部变化。同样也收到了接口1阶地址字节在Flash编程和核实。
端口2：
端口2是一个8位双向I / O端口与内部变化。这个端口2输出缓冲能沉/源四TTL的投入。当1就写信给端口2针将内部变化高,可作为输入。为输入变量, 端口2指针,将外部所牵引电流源,因为内部的变化。端口2放出高阶地址字节在从外部程序存储器和彰显出外部数据存储器存取期间使用16位址。在这种应用中,它使用的内在变化时间排放1秒。外部数据存储器存取期间使用8位址, 端口2放出内容的P2特殊功能登记。端口2也得到了高阶的地址位和一些控制信号在Flash编程和核实。
端口3：
端口3是一个8位双向I / O端口与内部变化。端口3输出缓冲能沉/源四TTL的投入。当1就写信给端口3指针将内部变化高,可作为输入。为输入变量, 端口3指针,将外部所牵引电流源(IIL)因变化。端口服务功能的3也不同特色的AT89C51
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空闲模式下
在空闲模式下,中央处理器把自己睡;所有的微外设保持活跃。该模式调用的软件。片上的内容的公绵羊、所有的特殊功能寄存器不变在这个模式下。空闲模式可以终止任何使中断或由硬件复位。应该指出的是,闲时终止一个硬件复位,设备通常程序执行,从简历在它停止两封,机器周期之前,内部重置算法以控制。样品的硬件抑制进入内部RAM在这种情况下,但进入港口大头针空洞。消除这种可能性一个出乎意料的写信给一个港口销闲时被终止,由复位、指导证明那个中调用一个空闲不应该写端口销或外部存储器。
Power-down模式
在power-down模式下,振子是结束了,但这个指令;用它召唤“power-down是最后的指令执行。这片上的公绵羊、特殊功能寄存器值,直到power-down保留自己的方式终止。唯一的退出,是一家五金power-down重置。SFRS重置重新定义,但不改变样品的公羊。重置不应该被激活之前VCC回到正常操作水平,都必须保持活跃的时间还不够久,允许振荡器来重新启动和稳定。
程序记忆锁位
当锁点,1是程序逻辑电平EA销样品并就搭在重置。如果这个装置是开机没有重置,门闩初始化一个随机值,认为直到重置价值被激活。加入是必要的值EA是一致的逻辑与当前水平销为设备正常运作
英文原文
Introduction of Programmable controllers
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From a simple heritage, these remarkable systems have evolved to not only replace electromechanical devices, but to solve an ever-increasing array of control problems in both process and nonprocess industries. By all indications, these microprocessor powered giants will continue to break new ground in the automated factory into the 1990s.
HISTORY
In the 1960s, electromechanical devices were the order of the day ass far as control was concerned. These devices, commonly known as relays, were being used by the thousands to control many sequential-type manufacturing processes and stand-along machines. Many of these relays were in use in the transportation industry, more specifically, the automotive industry. These relays used hundreds of wires and their interconnections to effect a control solution. The performance of a relay was basically reliable - at least as a single device. But the common applications for relay panels called for 300 to 500 or more relays, and the reliability and maintenance issues associated with supporting these panels became a very great challenge. Cost became another issue, for in spite of the low cost of the relay itself, the installed cost of the panel could be quite high. The total cost including purchased parts, wiring, and installation labor, could range from $30~$50 per relay. To make matters worse, the constantly changing needs of a process called for recurring modifications of a control panel. With relays, this was a costly prospect, as it was accomplished by a major rewiring effort on the panel. In addition these changes were sometimes poorly documented, causing a second-shift maintenance nightmare months later. In light of this, it was not uncommon to discard an entire control panel in favor of a new one with
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the appropriate components wired in a manner suited for the new process. Add to this the unpredictable, and potentially high, cost of maintaining these systems as on high-volume motor vehicle production lines, and it became clear that something was needed to improve the control process – to make it more reliable, easier to troubleshoot, and more adaptable to changing control needs.
That something, in the late 1960s, was the first programmable controller. This first ‘revolutionary’ system wan developed as a specific response to the needs of the major automotive manufacturers in the United States. These early controllers, or programmable logic controllers (PLC), represented the first systems that 1 could be used on the factory floor, 2 could have there ‘logic’ changed without extensive rewiring or component changes, and 3 were easy to diagnose and repair when problems occurred.
It is interesting to observe the progress that has been made in the past 15 years in the programmable controller area. The pioneer products of the late 1960s must have been confusing and frightening to a great number of people. For example, what happened to the hardwired and electromechanical devices that maintenance personnel were used to repairing with hand tools? They were replaced with ‘computers’ disguised as electronics designed to replace relays. Even the programming tools were designed to appear as relay equivalent presentations. We have the opportunity now to examine the promise, in retrospect, that the programmable controller brought to manufacturing.
All programmable controllers consist of the basic functional blocks shown in Fig.
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10. 1. We’ll examine each block to understand the relationship to the control system. First we look at the center, as it is the heart ( or at least the brain ) of the system. It consists of a microprocessor, logic memory for the storage of the actual control logic, storage or variable memory for use with data that will ordinarily change as a function power for the processor and memory. Next comes the I/O block. This function takes the control level signals for the CPU and converts them to voltage and current levels suitable for connection with factory grade sensors and actuators. The I/O type can range from digital (discrete or on / off), analog (continuously variable), or a variety of special purpose ‘smart’ I/O which are dedicated to a certain application task. The programmer is shown here, but it is normally used only to initially configure and program a system and is not required for the system to operate. It is also used in troubleshooting a system, and can prove to be a valuable tool in pinpointing the exact cause of a problem. The field devices shown here represent the various sensors and actuators connected to the I/O. These are the arms, legs, eyes, and ears of the system, including push buttons, limit switches, proximity switches, photosensors, thermocouples, RTDS, position sensing devices, and bar code reader as input; and pilot lights, display devices, motor starters, DC and AC drives, solenoids, and printers as outputs.
No single attempt could cover its rapidly changing scope, but three basic characteristics can be examined to give classify an industrial control device as a programmable controller.
(1) Its basic internal operation is to solve logic from the beginning of memory to some specified point, such as end of memory or end of program. Once the end is
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reached, the operation begins again at the beginning of memory. This scanning process continues from the time power is supplied to the time it is removed.
(2) The programming logic is a form of a relay ladder diagram. Normally open, normally closed contacts, and relay coils are used within a format utilizing a left and a right vertical rail. Power flow (symbolic positive electron flow) is used to determine which coil or outputs are energized or deenergized.
(3) The machine is designed for the industrial environment from its basic concept; this protection is not added at a later date. The industrial environment includes unreliable AC power, high temperatures (0 to 60 degree Celsius), extremes of humidity, vibrations, RF noise, and other similar parameters.
General application areas
The programmable controller is used in a wide variety of control applications today, many of which were not economically possible just a few years ago. This is true for two general reasons: 1 there cost effectiveness (that is, the cost per I/O point) has improved dramatically with the falling prices of microprocessors and related components, and 2 the ability of the controller to solve complex computation and communication tasks has made it possible to use it where a dedicated computer was previously used.
Applications for programmable controllers can be categorized in a number of different ways, including general and industrial application categories. But it is
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important to understand the framework in which controllers are presently understood and used so that the full scope of present and future evolution can be examined. It is through the power of applications that controllers can be seen in their full light. Industrial applications include many in both discrete manufacturing and process industries. Automotive industry applications, the genesis of the programmable controller, continue to provide the largest base of opportunity. Other industries, such as food processing and utilities, provide current development opportunities.
There are five general application areas in which programmable controllers are used. A typical installation will use one or more of these integrated to the control system problem. The five general areas are explained briefly below.
Description
The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of Flash programmable and erasable read only memory (PEROM). The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the industry-standard MCS-51 instruction set and pinout. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C51 is a powerful microcomputer which provides a highly-flexible and cost-effective solution to many embedded control applications.
Function characteristic
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The AT89C51 provides the following standard features: 4K bytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters, a five vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator and clock circuitry. In addition, the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port and interrupt system to continue functioning. The Power-down Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset.
Pin Description
VCC：Supply voltage.
GND：Ground.
Port 0：
Port 0 is an 8-bit open-drain bi-directional I/O port. As an output port, each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high impedance inputs .Port 0 may also be configured to be the multiplexed low order address/data bus during accesses to external program and data memory. In this mode P0 has internal pullups .Port 0 also receives the code bytes during Flash programming ,and outputs the code bytes during program verification . External pullups are required during program verification .
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Port 1
Port 1 is an 8-bit bi-directional I/O port with internal pullups .The Port 1 output buffers can sink/source four TTL inputs .When 1s are written to Port 1 pins they are pulled high by the internal pullups and can be used as inputs. As inputs ,Port 1 pins that are externally being pulled low will source current (IIL) because of the internal pullups .Port 1 also receives the low-order address bytes during Flash programming and verification.
Port 2
Port 2 is an 8-bit bi-directional I/O port with internal pullups .The Port 2 output buffers can sink/source four TTL inputs .When 1s are written to Port 2 pins they are pulled high by the internal pullups and can be used as inputs. As inputs ,Port 2 pins that are externally being pulled low will source current, because of the internal pullups .Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit addresses. In this application, it uses strong internal pullups when emitting 1s. During accesses to external data memory that use 8-bit addresses, Port 2 emits the contents of the P2 Special Function Register .Port 2 also receives the high-order address bits and some control signals during Flash programming and verification.
Port 3
Port 3 is an 8-bit bi-directional I/O port with internal pullups .The Port 3 output
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buffers can sink/source four TTL inputs .When 1s are written to Port 3 pins they are pulled high by the internal pullups and can be used as inputs. As inputs ,Port 3 pins that are externally being pulled low will source current (IIL) because of the pullups .
Idle Mode
In idle mode, the CPU puts itself to sleep while all the onchip peripherals remain active. The mode is invoked by software. The content of the on-chip RAM and all the special functions registers remain unchanged during this mode. The idle mode can be terminated by any enabled interrupt or by a hardware reset .It should be noted that when idle is terminated by a hard ware reset, the device normally resumes program execution ,from where it left off, up to two machine cycles before the internal reset algorithm takes control. On-chip hardware inhibits access to internal RAM in this event, but access to the port pins is not inhibited. To eliminate the possibility of an unexpected write to a port pin when Idle is terminated by reset, the instruction following the one that invokes Idle should not be one that writes to a port pin or to external memory.
Power-down Mode
In the power-down mode, the oscillator is stopped, and the instruction that invokes power-down is the last instruction executed. The on-chip RAM and Special Function Registers retain their values until the power-down mode is terminated. The only exit from power-down is a hardware reset. Reset redefines the SFRS but does not change the on-chip RAM. The reset should not be activated before VCC is restored
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to its normal operating level and must be held active long enough to allow the oscillator to restart and stabilize.
Program Memory Lock Bits
On the chip are three lock bits which can be left unprogrammed (U) or can be programmed (P) to obtain the additional features listed in the table below.
When lock bit 1 is programmed, the logic level at the EA pin is sampled and latched during reset. If the device is powered up without a reset, the latch initializes to a random value, and holds that value until reset is activated. It is necessary that the latched value of EA be in agreement with the current logic level at that pin in order for the device to function properly
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