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.
標簽：
C16x
微控制器
輸入信號
時序圖
上傳時間：
2014-04-02
上傳用戶：han_zh
The field of microelectromechanical systems (MEMS), particularly micromachinedmechanical transducers, has been expanding over recent years, and the productioncosts of these devices continue to fall. Using materials, fabrication processes, anddesign tools originally developed for the microelectronic circuits industry, newtypes of microengineered device are evolving all the time—many offering numerousadvantages over their traditional counterparts. The electrical properties of siliconhave been well understood for many years, but it is the mechanical properties thathave been exploited in many examples of MEMS. This book may seem slightlyunusual in that it has four editors. However, since we all work together in this fieldwithin the School of Electronics and Computer Science at the University of Southampton,it seemed natural to work together on a project like this. MEMS are nowappearing as part of the syllabus for both undergraduate and postgraduate coursesat many universities, and we hope that this book will complement the teaching thatis taking place in this area.
標簽：
MEMS
教材
上傳時間：
2013-10-16
上傳用戶：朗朗乾坤
兩種解決方案 Richard just finished building his new house. Now the only thing the house misses is a cute little wooden fence. He had no idea how to make a wooden fence, so he decided to order one. Somehow he got his hands on the ACME Fence Catalogue 2002, the ultimate resource on cute little wooden fences. After reading its preface he already knew, what makes a little wooden fence cute.
A wooden fence consists of N wooden planks, placed vertically in a row next to each other. A fence looks cute if and only if the following conditions are met:
?The planks have different lengths, namely 1, 2, . . . , N plank length units.
?Each plank with two neighbors is either larger than each of its neighbors or smaller than each of them. (Note that this makes the top of the fence alternately rise and fall.)
標簽：
house
the
finished
building
上傳時間：
2014-01-26
上傳用戶：541657925
