All inputs of the C16x family have Schmitt-Trigger input characteristics. These Schmitt-Triggers are intended to always provide proper internal low and high levels, even if anundefined voltage level (between TTL-VIL and TTL-VIH) is externally applied to the pin.The hysteresis of these inputs, however, is very small, and can not be properly USed in anapplication to suppress signal noise, and to shape slow rising/falling input transitions.ThUS, it mUSt be taken care that rising/falling input signals pass the undefined area of theTTL-specification between VIL and VIH with a sufficient rise/fall time, as generally USualand specified for TTL components (e.g. 74LS series: gates 1V/US, clock inputs 20V/US).The effect of the implemented Schmitt-Trigger is that even if the input signal remains inthe undefined area, well defined low/high levels are generated internally. Note that allinput signals are evaluated at specific sample points (depending on the input and theperipheral function connected to it), at that signal transitions are detected if twoconsecutive samples show different levels. ThUS, only the current level of an input signalat these sample points is relevant, that means, the necessary rise/fall times of the inputsignal is only dependant on the sample rate, that is the distance in time between twoconsecutive evaluation time points. If an input signal, for instance, is sampled throughsoftware every 10US, it is irrelevant, which input level would be seen between thesamples. ThUS, it would be allowable for the signal to take 10US to pass through theundefined area. Due to the sample rate of 10US, it is assured that only one sample canoccur while the signal is within the undefined area, and no incorrect transition will bedetected. For inputs which are connected to a peripheral function, e.g. capture inputs, thesample rate is determined by the clock cycle of the peripheral unit. In the case of theCAPCOM unit this means a sample rate of 400ns @ 20MHz CPU clock. This requiresinput signals to pass through the undefined area within these 400ns in order to avoidmultiple capture events.For input signals, which do not provide the required rise/fall times, external circuitry mUStbe USed to shape the signal transitions.In the attached diagram, the effect of the sample rate is shown. The numbers 1 to 5 in thediagram represent possible sample points. Waveform a) shows the result if the inputsignal transition time through the undefined TTL-level area is less than the time distancebetween the sample points (sampling at 1, 2, 3, and 4). Waveform b) can be the result ifthe sampling is performed more than once within the undefined area (sampling at 1, 2, 5,3, and 4).Sample points:1. Evaluation of the signal clearly results in a low level2. Either a low or a high level can be sampled here. If low is sampled, no transition willbe detected. If the sample results in a high level, a transition is detected, and anappropriate action (e.g. capture) might take place.3. Evaluation here clearly results in a high level. If the previoUS sample 2) had alreadydetected a high, there is no change. If the previoUS sample 2) showed a low, atransition from low to high is detected now.
上传时间： 2013-10-23
上传用户：copu
All inputs of the C16x family have Schmitt-Trigger input characteristics. These Schmitt-Triggers are intended to always provide proper internal low and high levels, even if anundefined voltage level (between TTL-VIL and TTL-VIH) is externally applied to the pin.The hysteresis of these inputs, however, is very small, and can not be properly USed in anapplication to suppress signal noise, and to shape slow rising/falling input transitions.ThUS, it mUSt be taken care that rising/falling input signals pass the undefined area of theTTL-specification between VIL and VIH with a sufficient rise/fall time, as generally USualand specified for TTL components (e.g. 74LS series: gates 1V/US, clock inputs 20V/US).The effect of the implemented Schmitt-Trigger is that even if the input signal remains inthe undefined area, well defined low/high levels are generated internally. Note that allinput signals are evaluated at specific sample points (depending on the input and theperipheral function connected to it), at that signal transitions are detected if twoconsecutive samples show different levels. ThUS, only the current level of an input signalat these sample points is relevant, that means, the necessary rise/fall times of the inputsignal is only dependant on the sample rate, that is the distance in time between twoconsecutive evaluation time points. If an input signal, for instance, is sampled throughsoftware every 10US, it is irrelevant, which input level would be seen between thesamples. ThUS, it would be allowable for the signal to take 10US to pass through theundefined area. Due to the sample rate of 10US, it is assured that only one sample canoccur while the signal is within the undefined area, and no incorrect transition will bedetected. For inputs which are connected to a peripheral function, e.g. capture inputs, thesample rate is determined by the clock cycle of the peripheral unit. In the case of theCAPCOM unit this means a sample rate of 400ns @ 20MHz CPU clock. This requiresinput signals to pass through the undefined area within these 400ns in order to avoidmultiple capture events.
上传时间： 2014-04-02
上传用户：han_zh
#include <reg51.h>#include<intrins.h> #define BUSY1 (DQ1==0) sbit DQ1 = P0^4; unsigned char idata TMP; unsigned char idata TMP_d; unsigned char f; void wr_ds18_1(char dat);unsigned char rd_ds18_1(); /***************延时程序，单位US,大于10US*************/void time_delay(unsigned char time){ time=time-10; time=time/6; while(time!=0)time--;} /*****************************************************//* reset ds18b20 *//*****************************************************/void ds_reset_1(void){ unsigned char idata count=0; DQ1=0; time_delay(240); time_delay(240); DQ1=1; return;}
上传时间： 2013-10-29
上传用户：sssnaxie
基于USB接口的数据采集模块的设计与实现Design and Implementation of USB-Based Data Acquisition Module路 永 伸(天津科技大学电子信息与自动化学院，天津300222)摘要文中给出基于USB接口的数据采集模块的设计与实现。硬件设计采用以Adpc831与PDIUSBDI2为主的器件进行硬件设计，采用Windriver开发USB驱动，并用Visual C十十6.0对主机软件中硬件接口操作部分进行动态链接库封装。关键词USB 数据采集Adpc831 PDNSBDI2 Windriver动态链接库Abstract T hed esigna ndim plementaitono fU SB-BasedD ataA cquisiitonM oduleis g iven.Th ec hips oluitonm ainlyw ithA dpc831a ndP DTUSBD12i sUSed for hardware design. The USB drive is developed场Wmdriver, and the operation on the hardware interface is packaged into Dynamic Link Libraries场Visual C++6.0. Keywords USB DataA cquisition Adttc831 PDfUSBD12 Windriver0 引言US B总 线 是新一代接口总线，最初推出的目的是为了统一取代PC机的各类外设接口，迄今经历了1.0,1.1与2.0版本3个标准。在国内基于USB总线的相关设计与开发也得到了快速的发展，很多设计者从各自的应用领域，用不同方案设计出了相应的装置[1,2]。数据采集是工业控制中一个普遍而重要的环节，因此开发基于USB接口的数据采集模块具有很强的现实应用意义。虽然 US B总线标准已经发展到2.0版本，但由于工业控制现场干扰信号的情况比较复杂，高速数据传输的可靠性不容易被保证，并且很多场合对数据采集的实时性要求并不高，开发2.0标准产品的成本又较1.1标准产品高，所以笔者认为，在工业控制领域，目前开发基于USB总线1.1标准实现的数据采集模块的实用意义大于相应2.0标准模块。
上传时间： 2013-10-23
上传用户：q3290766
摘 要 瞬态仿真领域的许多工作需要获得可视化数据, 仿真电路不能将输出参数绘制成图形时研究工作将受到很大影响. 而权威电路仿真软件PSpice 在这个方面不尽如人意. 本文提出了一种有效的解决办法: 通过MATLAB 编程搭建一个PSpice 与MATLAB 的数据接口,使PSpice输出数据文件可以导入到MATLAB中绘制图形. 这令我们能够很方便地获得数据的规律以有效地分析仿真结果, 这项技术对于教学和工程实践都有比较实际的帮助.关键词: 瞬态仿真 仿真程序 PSpice MATLAB 可视化数据The Data Transfer from Pspice to MATLABWu hao Ning yuanzhong Liang yingAbstract Many works in the area of transient simulation has shown how a emulator such asPSpice can be interfaced to an control analysis package such as MATLAB to get viewdata. Thepaper describes how such interfaces can be made USing the MATLAB programming. The platformas a typical platform will solve the problem that PSpice software sometimes can not draw the datato a picture. It can make US find the rule from numeroUS data very expediently, so we can analyzethe outcome of the simulation. And it also can be USed in the field of education.Keywords Transient Simulation Emulator PSpice MATLAB Viewdata1 引言科学研究和工程应用常需要进行电路仿真 PSpice可进行直流 交流 瞬态等基本电路特性分析 也可进行蒙托卡诺 MC 统计分析 最坏情况 Wcase 分析 优化设计等复杂电路特性分析 它是国际上仿真电路的权威软件 而MATLAB的主要特点有 高效方便的矩阵和数组运算 编程效率高 结构化面向对象 方便的绘图功能 用户使用方便 工具箱功能强大 两者各有着重点 两种软件结合应用 对研究工作有很重要的意义香港理工大学Y. S. LEE 等人首先将PSpice和MATLAB结合 开发了电力电子电路优化用的CAD 程序MATSPICE[6] 将两者相结合的关键在于 如何用MATLAB 获取PSpice的仿真数据 对此参考文献 6 里没有详细叙述 本文着重说明用MATLAB 读取PSpice仿真数据的具体方法本论文利用MATLAB对PSpice仿真出的数据处理绘制出后者无法得到或是效果不好的仿真图形 下面就两者结合使用的例子 进行具体说明
上传时间： 2013-10-20
上传用户：wuchunzhong
USB接口控制器参考设计,xilinx提供VHDL代码 USb xilinx vhdl ; This program is free software; you can redistribute it and/or modify ; it under the terms of the GNU General Public License as published by ; the Free Software Foundation; either version 2 of the License, or ; (at your option) any later version. ; ; This program is distributed in the hope that it will be USeful, ; but WITHOUT ANY WARRANTY; without even the implied warranty of ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ; GNU General Public License for more details. ; ; You should have received a copy of the GNU General Public License ; along with this program; if not, write to the Free Software ; Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
上传时间： 2013-10-12
上传用户：windgate
In today’s world of modular networking and telecommunications design, it is becomingincreasingly difficult to keep alignment with the many different and often changing interfaces,both inter-board and intra-board. Each manufacturer has their own spin on the way in whichdevices are connected. To satisfy the needs of our cUStomers, we mUSt be able to support alltheir interface requirements. For US to be able to make products for many cUStomers, we mUStadopt a modular approach to the design. This modularity is the one issue that drives the majorproblem of shifting our bits from one modular interface to another.
上传时间： 2013-11-25
上传用户：suicone
Abstract: The number of USes for microelectromechanical systems (MEMS) is growing—they allow US todo jobs once considered impossible. This tutorial explains the applications for MEMS and the increasingneed to provide precision control and drivers for these devices. Design and manufacturing considerationsare also discUSsed.
上传时间： 2013-11-12
上传用户：paladin
This book evolved over the past ten years from a set of lecture notes developed while teaching the undergraduate Algorithms course at Berkeley and U.C. San Diego. Our way of teaching this course evolved tremendoUSly over these years in a number of directions, partly to address our students' background (undeveloped formal skills outside of programming), and partly to reect the maturing of the eld in general, as we have come to see it. The notes increasingly crystallized into a narrative, and we progressively structured the course to emphasize the story line implicit in the progression of the material. As a result, the topics were carefully selected and clUStered. No attempt was made to be encyclopedic, and this freed US to include topics traditionally de-emphasized or omitted from most Algorithms books.
标签： Algorithms 算法
上传时间： 2013-11-11
上传用户：JamesB
注:1.这篇文章断断续续写了很久,画图技术也不精,难免错漏,大家凑合看.有问题可以留言. 2.论坛排版把我的代码缩进全弄没了,大家将代码粘贴到arduino编译器,然后按ctrl+T重新格式化代码格式即可看的舒服. 一、什么是PWM PWM 即Pulse Wavelength Modulation 脉宽调制波，通过调整输出信号占空比，从而达到改 变输出平均电压的目的。相信Arduino 的PWM 大家都不陌生，在Arduino Duemilanove 2009 中，有6 个8 位精度PWM 引脚，分别是3, 5, 6, 9, 10, 11 脚。我们可以使用analogWrite()控 制PWM 脚输出频率大概在500Hz 的左右的PWM 调制波。分辨率8 位即2 的8 次方等于 256 级精度。但是有时候我们会觉得6 个PWM 引脚不够用。比如我们做一个10 路灯调光， 就需要有10 个PWM 脚。Arduino Duemilanove 2009 有13 个数字输出脚，如果它们都可以 PWM 的话，就能满足条件了。于是本文介绍用软件模拟PWM。 二、Arduino 软件模拟PWM Arduino PWM 调压原理：PWM 有好几种方法。而Arduino 因为电源和实现难度限制，一般 使用周期恒定，占空比变化的单极性PWM。 通过调整一个周期里面输出脚高/低电平的时间比（即是占空比）去获得给一个用电器不同 的平均功率。 如图所示，假设PWM 波形周期1ms（即1kHz），分辨率1000 级。那么需要一个信号时间 精度1ms/1000=1US 的信号源，即1MHz。所以说，PWM 的实现难点在于需要使用很高频的 信号源，才能获得快速与高精度。下面先由一个简单的PWM 程序开始： const int PWMPin = 13; int bright = 0; void setup() { pinMode(PWMPin, OUTPUT); } void loop() { if((bright++) == 255) bright = 0; for(int i = 0; i < 255; i++) { if(i < bright) { digitalWrite(PWMPin, HIGH); delayMicroseconds(30); } else { digitalWrite(PWMPin, LOW); delayMicroseconds(30); } } } 这是一个软件PWM 控制Arduino D13 引脚的例子。只需要一块Arduino 即可测试此代码。 程序解析：由for 循环可以看出，完成一个PWM 周期，共循环255 次。 假设bright=100 时候，在第0~100 次循环中，i 等于1 到99 均小于bright，于是输出PWMPin 高电平； 然后第100 到255 次循环里面，i 等于100~255 大于bright，于是输出PWMPin 低电平。无 论输出高低电平都保持30US。 那么说，如果bright=100 的话，就有100 次循环是高电平，155 次循环是低电平。 如果忽略指令执行时间的话，这次的PWM 波形占空比为100/255，如果调整bright 的值， 就能改变接在D13 的LED 的亮度。 这里设置了每次for 循环之后，将bright 加一，并且当bright 加到255 时归0。所以，我们 看到的最终效果就是LED 慢慢变亮，到顶之后然后突然暗回去重新变亮。 这是最基本的PWM 方法，也应该是大家想的比较多的想法。 然后介绍一个简单一点的。思维风格完全不同。不过对于驱动一个LED 来说，效果与上面 的程序一样。 const int PWMPin = 13; int bright = 0; void setup() { pinMode(PWMPin, OUTPUT); } void loop() { digitalWrite(PWMPin, HIGH); delayMicroseconds(bright*30); digitalWrite(PWMPin, LOW); delayMicroseconds((255 - bright)*30); if((bright++) == 255) bright = 0; } 可以看出，这段代码少了一个For 循环。它先输出一个高电平，然后维持(bright*30)US。然 后输出一个低电平，维持时间((255-bright)*30)US。这样两次高低就能完成一个PWM 周期。 分辨率也是255。 三、多引脚PWM Arduino 本身已有PWM 引脚并且运行起来不占CPU 时间，所以软件模拟一个引脚的PWM 完全没有实用意义。我们软件模拟的价值在于：他能将任意的数字IO 口变成PWM 引脚。 当一片Arduino 要同时控制多个PWM，并且没有其他重任务的时候，就要用软件PWM 了。 多引脚PWM 有一种下面的方式： int brights[14] = {0}; //定义14个引脚的初始亮度，可以随意设置 int StartPWMPin = 0, EndPWMPin = 13; //设置D0~D13为PWM 引脚 int PWMResolution = 255; //设置PWM 占空比分辨率 void setup() { //定义所有IO 端输出 for(int i = StartPWMPin; i <= EndPWMPin; i++) { pinMode(i, OUTPUT); //随便定义个初始亮度,便于观察 brights[ i ] = random(0, 255); } } void loop() { //这for 循环是为14盏灯做渐亮的。每次Arduino loop()循环， //brights 自增一次。直到brights=255时候，将brights 置零重新计数。 for(int i = StartPWMPin; i <= EndPWMPin; i++) { if((brights[i]++) == PWMResolution) brights[i] = 0; } for(int i = 0; i <= PWMResolution; i++) //i 是计数一个PWM 周期 { for(int j = StartPWMPin; j <= EndPWMPin; j++) //每个PWM 周期均遍历所有引脚 { if(i < brights[j])\ 所以我们要更改PWM 周期的话，我们将精度（代码里面的变量：PWMResolution）降低就行，比如一般调整LED 亮度的话，我们用64 级精度就行。这样速度就是2x32x64=4ms。就不会闪了。
上传时间： 2013-10-08
上传用户：dingdingcandy
