毕业设计论文基于51单片机的外文翻译.doc

毕业设计（论文）基于51单片机外文翻译

毕业设计 论文 外文资料翻译外文出处： 外 文 .atmel/dyn/resources/prod ＿
documents/doc0287.pdf
51单片机在编程电路中应用
本应用指南说明了Atmel AT89C51是可在线可编程微控制器。它为电路编程提出了对应例子，程序修改需要在线编程支持。这类显示方法在应用程序中AT89C51单片机可经过电话线远程控制。该应用指南所描述电路只支持
5v电压下编程。此应用软件能够到Atmel进行下载。
总论当不在进行程序设计时候，在电路设计中AT89C51设计将变得透明化。
在编程期间必须重视EA/VPP这一脚。在不使用外部程序存放器应用程序中，这脚可能会永久接到VCC。应用程序使用外部程序存放器要求这一脚为低电平才能正常运行。
RST在编程期间必须为高电平。应该提供一个方法使得电路通入电源以后，使RST代替主要复位电路起到复位作用 。
在编程过程中，PSEN必须保持低电平，在正常运行期间绝不能使用。
ALE/ PROG在编程过程中输出低电平，在正常运行期间绝不能使用。
在编程过程中，AT89C51I / O端口是用于模式应用程序，地址和数据选
择，可能需要该控制器从应用电路隔离。怎样做到这一点取决于应用程序。
输入端口
在编程过程中，控制器必须与应用电路信号起源隔离。 带有三个输出状态缓冲区会在应用程序之间插入电路和控制器，同时在编程时缓冲区输出三种状态。一个多路复用器可用于信号源之间进行选择， 适适用于任何一方应用电路或编程控制器电路信号。
输出端口假如应用电路能够允许端口在编程过程中状态改变，则不需要改变电路。假如应用电路状态，必须事先在编程过程中保持不变，可能在控制器和
应用电路中插入锁存。锁存在编程期间是可用，并保留应用程序电路状态。
应用实例
应用是该AT89C51一个移动显示情况。此应用程序有在电路重新编程时将
结果以图表形式显示简单能力。文本显示被设计作为其硬件一部分，不能在无改编情况下改变。
显示文本可在4位DIP开关选择两种模式之一中进行。在第一个模式时候，进入一个字符从右边显示和快速移动，经过每个元素显示其在最终装配位置左侧。在
第二个模式，信息在信息窗口中右到左移动显示。这种模式与经常在股票价格显示器所使用方法类似。
输出包含四个DL1414T，4位17段积分解码器和驱动程序字母数字显示
器。这就产生了16名显示元素，每个数字有0-9显示能力，是大写字母，标点符号和一些字符。可显示字符ASCII 码，范围为20H-5FH。上电复位电路和一个6 MHz晶体振荡器完成应用软件程序。不论外部程序存放器或外部数据存放器都时可用。
支持应用程序修改
据推测，编程器在休眠时，既不会驱动，也不会加载应用程序。因为应用程序不使用外部程序存放器，EA/VPP 脚接 VCC 电源。复位电路被两种转换器改变状态，此转换器允许编程时RST接高电平。在基本应用时未使用PSEN和ALE/
PROG，是被程序员直接控制。编程器编程需要取得全部数据表中统计AT89C51I / O端口。编程器是与那些应用程序未使用控制器引脚相连，而这些应用程序引脚需要最低有效位四所产生地址是可取得，以下段所述。
由编程器生成最小四位地址是与 DIP 转换数据在控制器端口多路复用
请注意，加在开关上四个电阻在基本应用中并不是必须，因为AT89C51 端口上提供一个内部上拉电阻。
在应用程序正常运作时，控制器端口 0，1个分别在显示器上提供数据和控制信号。在编程和程序验证时，编程受端口0和端口2一部分控制。程序设计器连接端口0和1，没有缓冲，因为，在不活动时，它存在不影响应用程序正常运作。
透明锁存器被加在了控制器两个端口之间做输入控制。锁存持有显示控制信号在编程过程中不反应，从而消除端口0和2因为程序控制器活动造成操作失误。显示数据输入是不能被孤立，因为数据应用到输入被忽略时，控制信号无效。
AT89C51单片机复位电路，输入多路复用器和输出锁存器是由程序控制器生
成一个单一信号来控制。在编程过程中，复位键生效，多路开关信号输入，以及冻结显示锁存控制线。
为确保控制线显示在已知状态前锁定，AT89C51外部中止是用来允许程序控制器在复位之前向应用程序发出信号。应用程序固件响应中止显示一条消息，关闭显示控制线。
编程后，当复位生效，当锁存可视控制器端口输出高电平。因为显示控制输入不为高电平，直到新程序写入显示器内部不被打乱。即使这个应用程序是没有必要，它可能在一些应用中必须指出，在编程过程中不会扰乱外围电路状态
程序控制器
程序控制器生成地址，数据和控制信号，对嵌入到程序中AT89C51有主要作用。
程序控制器电路由一个AT89C51和一个RS - 232电平转换器组成。该控制器运行在11.0592兆HZ，此频率允许串口运行在一个标准波特率下。一个IM 232 线路驱动器/接收器产生RS - 232水平，而只需要5伏电源系统。
程序控制器所产生信号许多只需直接连接到AT89C51，无需缓冲。这些信号，在不活动时，不再是三种状态，但被接高电平。AT89C51端口1，2，3内部有大约 3000 欧姆上拉电阻，因为端口 0 没有内部上拉电阻，所以外部 10 千欧姆上拉电阻已经加上允许适当程序认证模式操作。示例应用程序在这种环境下可正常运行。假如有需要应用程序兼容性，程序发出信号可能在类似
74xx125三态缓冲缓冲区内缓冲。
AT89C51程序不使用外部程序或数据存放器，这需要牺牲所需要 I / O 引脚。这就要求程序代码和I / O缓冲区保持足够小以适合片上存放器。
商业电话线远程编程
编程器和前面描述显示应用是与经过调制解调器连接在远程站点电话线
相连。使用链接调制解调器个人电脑，用户能够上传包含一个新消息程序，这个信息被变成进了嵌入到应用程序AT89C51中。当编程完成后，应用程序执行新程序，它显示新信息。
当地配置
测试配置当地配置包含一台IBM个人电脑级计算机连接到与Hayes兼容，普罗米修斯1200波特调制解调器。选择此调制解调器，因为它是廉价可得。更加快调制解调器假如需要话可使用更加快速调制解调器，尽管一旦该文件传输时间低于 1 分钟，深入削减传输时间不会深入降低连接时间费用。更高传输速度可能优势是在一些高速调制解调器内自动错误检测和纠正。
Procomm Plus版本2.01，是一个商业数据通信软件包，用于配置调制解调器，建立通讯设置参数，并建立与远程调制解调器链接。 Procomm Plus包含所谓宏语言方面，它允许用户编写实现自定义文件传输协议脚本。一个简单脚本编写用来读取一个程序文件内容，并上传到远程编程器 。
文件传输协议（FTP）实施，是一个简单发送和等候，数据包导向协议。FTP模式发送和接收是用数字4和5，如流程图所表示。不在流程控制下发射器发送每个数据包，并等候响应。
在计算校验和时那个程序控制器（接收器）读取并剖析了数据包。假如计算
出校验和是有效，程序员经过发送一个ACK认可此数据包。假如校验和错误，程序员经过发送一个NAK来否定。当接收一个ACK后，发射器发送下一个数据包。假如传送者接收到NAK，它重新发送相同数据包。以这种方式传输，直到整个文件已被移交。
程序控制器可能经过发送一个CAN来响应数据包，CAN表明一个不可恢复错误发生，而发射机应立刻中止文件传输。假如程序员没有在有限时间内响应到一个数据包，发送器将重新发送相同数据包。发射器将继续重发，直到接收到一个有效反应，或者，超出文件传输被中止时间。每个数据包接收和经过程序员验证后，数据包中包含数据被加载到AT89C51单片机控制器编程。
编程后，数据从控制器读回并对接收数据包进行验证。成功审查表明，
成功程序设计，使程序员发送ACK给传送者。假如编程失败，程序员发送CAN 向传送者发送信号中止文件传输。
简单 FTP 降低了 AT89C51 程序在编程时使用内存量。因为 AT89C51 编程和擦除时间能够很轻易地吸收，FTP发送和等候性质允许跨包延迟。对程序验证支持是透明，不需要明确命令或结果代码，或转让其余数据。
上传到程序控制器文件是用英特尔MCS- 51软件开发包来创建。在包中包含了MCS - 51宏汇编，MCS - 51单片机Relocator和连接器，以及一个有用
工具，OH。OH将8051绝对目标文件转换为为等效ASCII十六进制目标文件。
远程配置
在测试配置中远程配置包含显示应用程序和程序员电路，如前所述，连接到一个与Hayes兼容普罗米修斯1200波特调制解调器。在正常操作时，应用程序执行其内部程序，而调制解调器和程序员监测来电电话线。
通话被检测到并连接建立后，程序器强迫暂停其程序执行。新程序就被下载并嵌入到应用程序中AT89C51编程。当编程完成后，应用软件程序获准开始其新程序执行，而程序控制器返回监督下一个通话电话线。
程序控制输出无效时程序控制器上电，允许应用程序正常运行。在配置调制解调器接听来电后，程序控制器停顿工作。是程序控制器不会影响到程序直到一个新程序应用程序被下载。程序员经过发送控制在串行接口上ASCII命令字符串来控制调制解调器，
对此调制解调器响应海斯式调制解调器ASCII数字代码。该软件是专为与海斯兼容使用调制解调器，其中包含这里使用1200普罗米修斯ProModem。
串行接口，程序员经过它连接到调制解调器，它支持两个握手信号，DTR和
DSR。上电时，程序控制器判定 DTR，断定为 DTR 后调制解调器响应。假如调制解调器不响应任何命令，包含命令挂断，程序控制器抬高DTR点位，强制调制解调器下降。
当程序控制器停顿工作后，监测调制解监听电话线，等候来电呼叫。当检测到输入，调制解调器响应并试图与输入建立通信。假如建立了连接，调制解调器发送一个代码，唤醒程序控制器。程序控制器验证连接代码，并开始审查有效数据包报头。
传入数据包必须在少于30秒内抵达，不然调制解调器挂断和程序控制器继续停顿工作，等候下一次呼叫。假如来电挂断，在得到下一次呼叫之前，三十秒时间必须终止。在复位延迟时间传入是被忽略。
假如复位延迟时间结束之前收到一个有效数据包报头，程序控制器将尝试读取和验证传入数据包。在数据包接收过程中任何时间，无效字符，奇偶校验错误或超时时间内接待字符将造成部分数据包被宣告无效，并丢弃。
两个数据包类型定义：数据和最终文件。数据包包含五个领域，除了包报头，
是一个可变长度数据字段。数据字段包含程序数据在应用程序中被写入在
AT89C51控制器。负载地址字段中包含数据写入地址。末端文件包中包含与数据包相同领域文件，但该数据字段是空。这包类型对程序控制器具备特殊意义，以下所述。任何包含有效文种数据包，统计长度或校验和无效。程序数据在一个无效数据包被丢弃处理过程中被积累。编程器给传送者发送一个NAK作为信号数据包接收和恢复为一个有效数据包报头审查警示信号。
第一个有效数据接收引发编程器中止应用程序控制器。该控制器中止响应放弃其正在运行程序，并显示一条消息，表明程序已经被代替。假如这是因为接收了末端文件或者是电源触发从而接收第一个有效数据包，利用必要控制信号去除在应用控制器内记忆程序。然后编程器在程序模式中放置控制器。
当接收到第一个和其后有效数据程序包时，将它们分开，它们包含数据被编程到程序包负载地址域中地址中应用控制器内。编程后，从控制器内将数据读回并与接收到数据包中数据进行比较。成功核查表明，方案是成功，造成编程器向传送者发送ACK信号。因为30秒复位延迟，编程器重新对有效数据包报头进行测试。
假如编程失败，编程器向传送者发送信号CAN中止文件传输。调制解调器掉线，程序器继续休眠等候下一次呼叫。应用控制在程序模式中被保留，用以阻止它包含不完整或无效程序。
主要是要注意，无效数据包永远不会规划到应用程序控制器。这么做将要求错误被纠正之前，编程器中记忆程序被彻底抹掉，造成先前全部数据不可恢复。
依照末端文件接收，编程器向闲置状态电源返回其控制输出，允许应用程序控制器，开始执行新程序。然后编程器在三十秒延迟之下重新开始对一个数据包报进行审查。假如一个有效数据包在30秒延迟之前接收，另一个只能被接收一个有效末端文件而终止程序循环开始执行。
假如复位在收有效末端文件之前终止，那么调制解调器会掉线，编程器停顿工作，等候下一次传入。在这种情况下应用控制器被保留在程序设计模式，以预防它执行这个程序。要返回应用程序正常运行，另一个传入必须被接收，一个有效程序文件被上传，由末端文件包终止。
AT89C51 In-Circuit Programming
This application note illustrates the in-circuit programmability of the Atmel AT89C51 Flash-based microcontroller. Guidelines for the addition of in-circuit programmability to AT89C51 applications are presented along with an application example and the modifications to it required to support in-circuit programming. A method is then shown by which the AT89C51 microcontroller in the application can be reprogrammed remotely, over a commercial telephone line. The circuitry described in this application note supports five volt programming only, requiring the use of an AT89C51-XX-5. The standard AT89C51 requires 12 volts for programming. The software for this application may be obtained by downloading from Atmel’s
General Considerations
Circuitry added to support AT89C51 incircuit programming should appear transparent to the application when programming is not taking place.
EA/VPP must be held high during programming. In applications which do not utilize external program memory, this pin may be permanently strapped to VCC. Applications utilizing external program memory require that this pin be held low during normal operation.
RST must be held active during programming. A means must be provided for overriding the application reset circuit, which typically asserts RST only briefly after power is applied.
PSEN must be held low during programming, but must not be driven during normal operation.
ALE/PROG is pulsed low during programming, but must not be driven during normal operation.
During programming, AT89C51 I/O ports are used for the application of mode select, addresses and data, possibly requiring that the controller be isolated from the application circuitry. How this is done is application dependent and will be addressed here only in general terms. Port Used for Input
During programming, the controller must be isolated from signals sourced by the application circuitry. A buffer with threestate outputs might be inserted between the application circuitry and the controller, with the buffer outputs three-stated when programming is enabled. Alternately, a multiplexer might be used to select between signal sources, with signals applied to the controller by either the application circuitry or the programmer circuitry.
Port Used for Output
No circuit changes are required if the application circuitry can tolerate the state changes which occur at the port during programming. If the prior state of the application circuitry must be maintained during programming, a latch might be inserted between the controller and the application circuitry. The latch is enabled during programming, preserving the state of the application circuitry.
An Application Example
The AT89C51 application shown in Figure 1 is an implementation of a moving display. This application was selected for its simplicity and ability to show graphically the results of in-circuit reprogramming. The text to be displayed is programmed into the controller as part of its firmware, and cannot be changed without reprogramming the device.
The displayed text is presented in one of two modes selected by the four-position DIP switch. In the first mode, one character at a time enters the display from the right and moves quickly to the left through each element of the display to its final position in the assembled message. In the second mode, the message moves through the display, from right to left, with the display acting as a window onto the message. This mode is familiar as the method often used in displays of stock prices.
The output consists of four DL1414T, four-digit, 17-segment alphanumeric displays with integral decoders and drivers. This yields 16 total display elements, each capable of displaying digits 0-9, the upper case alphabet, and some punctuation characters. The displayable character codes are ASCII 20H-5FH.
A power-on reset circuit and a 6-MHz crystal oscillator complete the application. Neither external program memory nor external data memory is used.
Modifications to the Application to Support
In-Circuit Programming Figure 2 shows the application modified for in-circuit programming.
It is assumed that the programmer, when inactive, will neither drive nor excessively load the application. Since the application does not use external program memory, EA/VPP on the controller is connected to VCC. This meets the requirement for programming.
The reset circuit has been modified by the addition of twotransistors, which allow RST on the controller to be forced high by the programmer.
PSEN and ALE/PROG, unused in the basic application, areunder the direct control of the programmer.
Programming requires programmer access to all of the four AT89C51 I/O ports, as documented in the data sheet. The programmer is connected directly to those controller pins which are unused by the application, while access to pins used by the application requires special treatment, as explained in the following paragraphs.
The least significant four bits of the address generated by the programmer are multiplexed onto port one of the controller with the data from the DIP switch. Note that the four resistors added at the switch are not required in the basic application, since the AT89C51 provides internal pull-ups on port one.
During the normal operation of the application, controller ports zero and two provide data and control signals respectively to the displays. During programming and program verification, the programmer asserts control of port zero and part of port two. The programmer is connected to ports zero and two without buffering, since, when inactive, its presence does not affect the normal operation of the application.
A transparent latch has been added between port two of the controller and the display control inputs. The latch holds the display control signals inactive during programming, which eliminates erratic operation of the displays due to programmer activity on ports zero and two. No isolation of the display data inputs is required, since data applied to the inputs is ignored when the control signals are inactive.
The AT89C51 reset circuit, input multiplexer and output latch are controlled by a single signal generated by the programmer. During programming, reset is asserted, the multiplexer switches inputs, and the latch freezes the display control lines.
To ensure that the display control lines are in a known state before they are latched, an AT89C51 external interrupt is used to allow the programmer to signal the application before asserting reset. The application firmware responds to the interrupt by displaying a message and deactivating the display control lines.
After programming, when reset is deasserted, the controller ports are high as the latch becomes transparent. Since the display control inputs are inactive high, the display contents are not disturbed until the new program writes the display. Although not essential to this application, it might be imperative in some applications that the state of the peripheral circuitry not be disturbed during programming.
The Programmer
The programmer Figure 3 generates the addresses, data and control signals necessary to program the AT89C51 embedded in the application.
The programmer circuitry consists of an AT89C51 and an RS-232 level translator. The controller runs at 11.0592 MHz, which allows the serial port to operate at a number of standard baud rates. A im 232 line driver/receiver produces RS-232 levels at the serial interface while requiring only a five volt supply.
Many of the signals generated by the programmer are connected directly, without buffering, to the AT89C51 in the application. These signals, when inactive, are not threestated, but are pulled high. The AT89C51 has internal pull-ups of approximately three Kohms on ports one, two and three. Because port zero does not have internal pull-ups, external pull-ups of ten Kohms have been added to permit proper operation of program verification mode. The sample application operates correctly in this environment. If required for compatibility with an application, programmer signals may be buffered with three-state buffers similar to the 74xx125.
The AT89C51 in the programmer does not utilize external program or data memory, which would require sacrificing needed I/O pins. This requires that program code and I/O buffers be kept small enough to fit in on-chip memory.
Remote Programming Over a Commercial
Telephone Line
The programmer and display application described previously are connected to a phone line via a modem at a remote site. Using a personal computer with a modem, a user can upload a new program containing a new message, which is programmed into the AT89C51 embedded in the application. When programming is complete, the application executes the new program, which displays the new message.
Local Station
The local station in the test configuration consists of an IBM PC AT-class computer connected to a Hayes-compatible, Prometheus 1200 baud modem. The modem was selected because it was inexpensive and available. A faster modem may be used if desired, although once the file transmission time is reduced below one minute, further reductions in transmission time do not further reduce connect time charges. A possible advantage to higher transmission speeds is the automatic error detection and correction available in some high speed modems.
Procomm Plus version 2.01, a commercial data communications package, is used to configure the modem, se