time-clocks

clock函数的使用方法clock函数是C语言中的一个库函数，用于计算程序运行时间。

它的使用方法相对简单，但需要掌握一定的编程基础知识。

在本文中，我们将详细介绍clock函数的使用方法。

1. 引入头文件在使用clock函数之前，必须先引入头文件。

在C语言中，我们可以通过以下语句引入头文件：#include <time.h>这条语句将time.h头文件引入到我们的程序中，使我们可以使用time相关的函数和变量。

2. 调用clock函数在程序中调用clock函数非常简单。

我们只需要使用以下语句即可：clock_t start_time = clock();这条语句将获取当前时间，并将其保存在一个名为start_time的变量中。

值得注意的是，clock函数的返回值类型为clock_t，所以start_time的类型也是clock_t。

3. 运行要测试的程序接下来，我们可以运行我们要测试的程序。

在程序运行之后，我们可以再次调用clock函数，获取程序结束时间：clock_t end_time = clock();同样，这条语句将获取当前时间，并将其保存在一个名为end_time的变量中。

4. 计算程序运行时间接下来我们需要通过简单的数学运算计算程序的运行时间。

我们只需要将end_time减去start_time，然后将差值除以CLOCKS_PER_SEC即可。

例如：double total_time = (double)(end_time - start_time) /CLOCKS_PER_SEC;这条语句将计算程序的总运行时间，并将结果保存在一个名为total_time的变量中。

注意，我们需要将end_time和start_time的差值强制转换为double类型，以避免出现整数除法的问题。

此外，CLOCKS_PER_SEC是一个常量，表示每秒钟的时钟嘀嗒数。

我们需要将差值除以该常量，才能得到程序的实际运行时间。

认识钟表的题30道可打印英文回答：Introduction:Clocks are an essential part of our daily lives. They help us keep track of time and manage our schedules. In this article, I will share 30 printable clock-related questions and answers. So, let's dive in and explore the fascinating world of clocks!1. How does a clock work?A clock works by using a power source, such as a battery or electricity, to move the hands or digits on the clock face. The movement of the hands or digits indicates the passage of time.2. What are the different types of clocks?There are various types of clocks, including analog clocks, digital clocks, wall clocks, alarm clocks, and grandfather clocks. Each type has its own unique features and functions.3. Can you give an example of an analog clock?Sure! An analog clock is a traditional clock with hour, minute, and sometimes second hands. It usually has a circular face with numbers or Roman numerals to indicate the time. An example of an analog clock is the classic round wall clock found in many homes and offices.4. What is a digital clock?A digital clock displays the time using digits, usually in the format of hours and minutes. It is commonly found on electronic devices such as smartphones, computers, and microwaves.5. How accurate are clocks?Clocks can vary in accuracy. Some clocks, like atomic clocks, are incredibly accurate and can measure time to within a fraction of a second. Others, such as mechanical clocks, may have slight variations and require periodic adjustments.6. Can you explain the concept of time zones?Time zones are regions with the same standard time. They are used to simplify timekeeping and ensure that people in different parts of the world are on a similar schedule. For example, if it's 12:00 PM in New York, itwill be a different time in London due to the time zone difference.7. What is the significance of daylight saving time?Daylight saving time is the practice of adjusting the clock forward by one hour during the summer months to extend daylight in the evenings. This allows people to make better use of natural daylight and save energy.8. How do you read a clock?To read a clock, you need to identify the position of the hour hand, minute hand, and sometimes the second hand. The hour hand points to the current hour, the minute hand indicates the minutes, and the second hand shows the seconds.9. Are there any idioms or phrases related to clocks?Yes, there are several idioms and phrases related to clocks. For example, "beat the clock" means to finish a task before a deadline, and "around the clock" means continuously or without stopping.10. Can you give an example of using an idiom related to clocks?Certainly! Let's say I have a project due tomorrow, but I'm running out of time. I might say, "I need to work around the clock to finish this on time!"中文回答：介绍：钟表是我们日常生活中不可或缺的一部分。

闹钟的作用英语作文Title: The Significance of Alarm Clocks。

Introduction:Alarm clocks play an essential role in our daily lives, serving as reliable tools to wake us up and ensure we start our day on time. Their significance extends beyond mere timekeeping devices, influencing our productivity, punctuality, and overall well-being.Body:1. Ensuring Punctuality: 。

Alarm clocks are indispensable for ensuring punctuality in our routines. Whether it's waking up for work, school, or appointments, these devices serve as dependable reminders, helping us adhere to schedules and meet commitments promptly. Without alarm clocks, many of uswould struggle to wake up consistently at the required times, leading to tardiness and disruptions in our daily lives.2. Promoting Productivity:By waking us up at predetermined times, alarm clocks help jumpstart our productivity each day. They provide a sense of structure and discipline, encouraging us to get out of bed and begin our tasks efficiently. This regularity fosters a productive mindset, allowing us to tackle our responsibilities with focus and determination. Moreover, the act of setting an alarm the night before can serve as a psychological cue, mentally preparing us for the day ahead and setting a positive tone for our activities.3. Maintaining Health and Well-being:Adequate sleep is crucial for overall health and well-being, and alarm clocks play a vital role in maintaining healthy sleep-wake cycles. By ensuring that we wake up at consistent times, these devices help regulateour internal body clocks, promoting better sleep qualityand overall health. Furthermore, alarm clocks can be programmed to wake us up gradually with gentle sounds or light, mimicking the natural sunrise and easing thetransition from sleep to wakefulness. This gradual awakening can reduce feelings of grogginess and improve our mood and energy levels throughout the day.4. Building Discipline and Responsibility:The act of setting and adhering to alarm schedules instills discipline and responsibility in individuals ofall ages. It teaches us the importance of planning aheadand honoring our commitments, traits that are essential for success in both personal and professional spheres. Moreover, consistent use of alarm clocks fosters a sense of accountability, as we take ownership of our time and prioritize our obligations accordingly.5. Facilitating Time Management:Effective time management is a cornerstone ofsuccess in any endeavor, and alarm clocks serve as valuable tools in this regard. By dividing our day into manageable segments and allocating time for various tasks, we can optimize our productivity and accomplish more in less time. Alarm clocks help us adhere to predetermined schedules, ensuring that we allocate sufficient time to essential activities such as work, study, exercise, and relaxation. This structured approach to time management minimizes procrastination and maximizes efficiency, enabling us to make the most of each day.Conclusion:In conclusion, alarm clocks play a multifaceted role in our lives, transcending their basic function of waking usup in the morning. From promoting punctuality and productivity to maintaining health and fostering discipline, these devices are indispensable tools for managing our time and achieving our goals. By recognizing the significance of alarm clocks and incorporating them into our daily routines, we can enhance our efficiency, well-being, and overall quality of life.。

关于时间点钟的英语作文Title: Exploring the Significance of Time in Our Lives。

Time is an abstract concept that governs our lives in profound ways. Among the various ways we measure and perceive time, one of the most ubiquitous is the clock. Clocks are not just instruments for telling time; they are symbolic representations of our relationship with time itself. In this essay, we delve into the significance of time as represented by the clock.First and foremost, the clock serves as a practicaltool for organizing our daily activities. From the momentwe wake up to the time we go to bed, our lives arestructured around the ticking hands of the clock. Itdictates when we eat, work, sleep, and engage in leisure activities. Without the clock to regulate our schedules, chaos would ensue, highlighting its indispensable role in modern society.Beyond its practical utility, the clock also holds symbolic significance. It serves as a constant reminder of the passage of time and the fleeting nature of life itself. Every tick of the clock signifies a moment lost to the past, urging us to make the most of the time we have. The inevitability of time's passage instills a sense of urgency, motivating us to pursue our goals and aspirations beforeit's too late.Moreover, different cultures and civilizations throughout history have imbued the clock with various symbolic meanings. In some cultures, the clock represents order and discipline, reflecting societal values of punctuality and efficiency. In others, it symbolizes mortality, reminding us of our limited time on Earth. Regardless of interpretation, the clock serves as auniversal symbol of humanity's attempt to make sense of the passage of time.Interestingly, the invention of the clock has also influenced our perception of time itself. Before the advent of precise timekeeping devices, time was perceived in amore fluid and subjective manner, dictated by natural phenomena such as the movement of the sun and stars. However, with the introduction of clocks, time became standardized and quantifiable, leading to a more regimented approach to time management.Furthermore, the evolution of clock technology has had far-reaching implications for society. The invention of mechanical clocks in medieval Europe revolutionized commerce, facilitating trade and economic growth. The subsequent development of pendulum clocks and then quartz clocks further refined timekeeping accuracy, culminating in the atomic clock, which is accurate to within a few billionths of a second.In the digital age, the proliferation of digital clocks and smartphones has made time even more omnipresent in our lives. We are constantly bombarded with notifications, reminders, and alarms, further emphasizing the importance of time management. However, this constant exposure to time can also lead to stress and anxiety, as we feel pressured to constantly optimize our time and productivity.In conclusion, the clock is much more than a mere instrument for telling time; it is a symbol of humanity's relationship with time itself. From its practical utility in organizing our daily lives to its symbolic significance in representing the passage of time, the clock plays a central role in shaping our perception of time. As we continue to navigate the complexities of modern life, it is essential to reflect on the profound significance of time as represented by the clock.。

钟的英语作文Clocks: A Brief History and Their Importance in Modern Life。

Clocks have been an essential part of human life for centuries. From the earliest sundials to the modern digital watches, clocks have evolved and adapted to suit the needs of society. In this article, we will explore the history of clocks, their various types, and their importance in modern life.The earliest form of clock was the sundial, which was used by the ancient Egyptians and Greeks over 3,500 years ago. Sundials were simple instruments that used theposition of the sun to tell time. They consisted of a flat surface with a raised gnomon that cast a shadow onto the surface, indicating the time of day. However, sundials could only be used during the day and were not accurate during cloudy or rainy weather.The next major advancement in clock technology was the water clock, which was invented by the ancient Greeks around 325 BC. Water clocks used the flow of water to measure time. They consisted of a container with a small hole at the bottom, which allowed water to flow out at a constant rate. The water level in the container would gradually decrease, indicating the passage of time. Water clocks were much more accurate than sundials and could be used both day and night.In the Middle Ages, mechanical clocks were developed in Europe. These clocks used a pendulum or balance wheel to regulate the movement of the clock hands. Mechanical clocks were much more accurate than water clocks and could be made smaller, allowing them to be used in homes and churches.In the 20th century, electronic clocks were developed, which used electricity to regulate their movement. Electronic clocks were even more accurate than mechanical clocks and could be made even smaller. Today, most clocks are digital and use quartz crystals to keep time.Clocks are used for a variety of purposes in modern life. They are used to tell time, of course, but they also have many other uses. Clocks are used in schools to keep students on schedule, in factories to regulate production, and in hospitals to monitor patients' vital signs. Clocks are also used in sports to time events and intransportation to keep schedules on track.In conclusion, clocks have come a long way since the ancient sundials. From water clocks to mechanical clocks to electronic clocks, they have evolved and adapted to suit the needs of society. Today, clocks are an essential part of modern life, used for a variety of purposes. Without clocks, our lives would be much more chaotic and disorganized.。

认识钟表专项训练题可打印英文回答：Clocks are an essential part of our daily lives. They help us keep track of time and ensure that we are punctual for our appointments and deadlines. In this specialized training, I will provide you with printable clock exercises to help you improve your understanding of clocks and time.Firstly, let's start with the basics. A clock consists of two hands the hour hand and the minute hand. The hour hand is shorter and moves slowly, indicating the current hour. The minute hand is longer and moves faster, showing the minutes. Together, they work in harmony to tell us the time.To practice reading clocks, I have prepared a set of printable exercises. Each exercise will display a clock face with the hour and minute hands in different positions. Your task is to determine the time shown on the clock andwrite it down. For example, if the hour hand is pointing at 3 and the minute hand is pointing at 12, the time would be 3 o'clock. Take your time and try to solve each exercise accurately.In addition to reading clocks, it is also important to understand the concept of time intervals. Time intervals refer to the duration between two specific points in time. For instance, if an event starts at 2 o'clock and ends at 4 o'clock, the time interval would be 2 hours.To practice calculating time intervals, I have included exercises that require you to determine the duration between two given times. For example, if an event starts at 9 o'clock and ends at 11 o'clock, the time interval would be 2 hours. These exercises will help you sharpen your time calculation skills.Furthermore, I have included exercises that involve converting time between different units. This will help you become more familiar with various time measurements. For instance, converting minutes to hours or hours to seconds.These exercises will provide you with a comprehensive understanding of time and its measurements.Lastly, I have included some word problems related to clocks and time. These problems will test your ability to apply your knowledge of clocks in real-life scenarios. For example, calculating the time it takes for someone to travel from one place to another given their average speed and distance.中文回答：钟表是我们日常生活中不可或缺的一部分。

用英语介绍时钟的作文英文回答：Clocks are an essential part of our daily lives. They help us keep track of time and ensure that we are punctual for our appointments and commitments. There are various types of clocks, ranging from traditional analog clocks to modern digital clocks. Each type has its own unique features and advantages.Analog clocks have been around for centuries and are still widely used today. They typically have a circular face with numbered hour markers and rotating hands. The hour hand indicates the hour, while the minute hand shows the minutes. Some analog clocks also have a second hand that moves continuously around the clock face. One of the advantages of analog clocks is that they provide a visual representation of the passage of time. By glancing at the position of the hands, we can quickly determine the approximate time. For example, if the minute hand ispointing at the 6 and the hour hand is between the 3 and the 4, we can infer that it is around 3:30. Analog clocks are also often considered more aesthetically pleasing and can serve as decorative items in our homes or offices.On the other hand, digital clocks have become increasingly popular in recent years. Instead of using rotating hands, digital clocks use electronic displays to show the time in numerical format. They often have additional features such as alarms, timers, and even temperature displays. Digital clocks are known for their accuracy and precision. They provide an exact representation of the time, down to the second. This can be particularly useful in situations where precise timing is required, such as in scientific experiments or sports events. Additionally, digital clocks are often equipped with backlighting, making them easier to read in the dark. For example, if I wake up in the middle of the night and want to check the time, I can simply glance at the digital clock on my bedside table without having to turn on the lights.中文回答：时钟是我们日常生活中不可或缺的一部分。

有关钟表的时间类英语词汇Timekeeping in English: A Detailed Look at Clock and Watch Terminology.The English language is rich in vocabulary, and nowhere is this more evident than in the terminology surrounding the measurement of time. From the tick of a clock to the sweep of a second hand, we have a vast array of words and phrases to describe the passing of moments, hours, days, and years. In this article, we'll delve into theintricacies of timekeeping in English, exploring various terms related to clocks, watches, and the various units of time.1. Basic Units of Time.Second: The smallest common unit of time, typically represented by a hand on a clock or watch that completes one revolution every 60 seconds.Minute: Sixty seconds, represented by a longer hand on a clock or watch that completes one revolution every 60 minutes.Hour: Sixty minutes, typically marked by numbers on a clock face from 1 to 12 (or 24 in a 24-hour format).Day: Twenty-four hours, the period of time from one midnight to the next.Week: Seven days, traditionally associated with the seven days of creation in Genesis.Month: The duration of the moon's phases, ranging from 28 to 31 days depending on the calendar.Year: Approximately 365.25 days, representing the time it takes the Earth to orbit the Sun once. Leap years add an additional day (February 29th) to compensate for the quarter-day difference.2. Types of Clocks and Watches.Wall Clock: A clock designed to be hung on a wall, typically used in homes and offices to keep track of time.Mantel Clock: A small, decorative clock often placedon a mantelpiece or shelf.Grandfather Clock: A large, freestanding clock with a pendulum and typically wooden casing, often used as a decorative piece in a home.Wristwatch: A timepiece worn on the wrist, typically with a metal band.Pocket Watch: A small clock designed to be carried ina pocket, typically with a chain for attachment to clothing.Stopwatch: A time-measuring device with a start, stop, and reset function, often used by athletes and coaches.Digital Clock: A clock that displays time in a numerical format, often with additional features likealarms or timers.3. Clock and Watch Parts.Face: The flat surface of a clock or watch where the time is displayed.Dial: The circular plate on a clock or watch face that displays the numbers and other markings indicating the time.Hands: The metal or plastic rods that move to indicate the time on a clock or watch. The longest is usually the hour hand, followed by the minute hand and then the second hand.Bezel: The frame that surrounds the dial on a watch or clock.Case: The outer housing of a clock or watch,protecting the internal mechanisms.Crown: The knob on a watch used to set the time andadjust other functions.Back: The rear part of a clock or watch case, often removable to access the internal mechanisms.4. Timekeeping Terms.Time Zone: A geographical area that observes a uniform standard time.UTC (Coordinated Universal Time): The international standard for timekeeping, used to synchronize clocks worldwide.Daylight Saving Time: A system of adjusting clocks forward by one hour during the summer months to maximize daylight hours.Atomic Clock: A highly accurate clock that uses atomic vibrations to measure time, typically used for scientific and navigational purposes.Quartz Clock: A type of clock that uses a quartz crystal to keep time, offering greater accuracy than mechanical clocks.Chronometer: A watch or clock specifically designed and tested for precision and reliability, often used by mariners and navigators.5. Expressions Related to Time.Tick-tock: The sound made by a clock or watch as it ticks forward.Time flies: An expression used to describe how time passes quickly.Time stands still: An expression used to describe a moment that feels suspended or frozen in time.Time is money: An adage expressing the value of time and its importance in achieving goals.Time will tell: An expression used to indicate that only time can reveal the outcome of a situation or event.In conclusion, the English language is rich with terms and expressions related to timekeeping. From the basicunits of time to the intricate parts of clocks and watches, we have a vast vocabulary to describe the ever-passing moments of our lives. From tick-tock to time flies, these expressions further illustrate the cultural and contextual importance of time in our daily lives.。

英语作文：ClocksClocks are one of the most important inventions in human history. They have been around for centuries, and have been used to measure time, from the minute to the millennium. Clocks have been used to plan activities, to coordinate events, and to measure performance.Clocks come in a variety of shapes and sizes, from the traditional mechanical clocks to the modern digital clocks. The earliest clocks were created in the ancient world, and were used to measure the passing of time. As technology advanced, clocks became more accurate and reliable. The invention of the quartz clock in the 19th century revolutionized timekeeping, as it was the first clock that could measure time to the nearest second.Today, clocks are used in almost every aspect of life. From the wristwatch to the atomic clock, they are used to measure time, to set alarms, and to keep track of events. Clocks are also used in many industries, from aviation to finance, to ensure accuracy and efficiency.Clocks have come a long way since their invention, and have become an integral part of our lives. They have allowed us to measure time, to plan our lives, and to keep track of events. Clocks will continue to be a part of our lives for centuries to come.。

用英语介绍时钟的作文英文回答：Clock is an essential part of our daily lives. It helps us keep track of time and ensures that we are punctual for our appointments and commitments. It is a device that displays the time in hours, minutes, and sometimes even seconds. The invention of the clock has revolutionized the way we organize our lives and has become an integral part of our routines.One of the most common types of clocks is the analog clock. It has a round dial with numbers from 1 to 12 and two hands, one for hours and the other for minutes. The hour hand moves slowly while the minute hand moves faster. This allows us to easily read the time by looking at the position of the hands on the dial. For example, if the hour hand is pointing at 3 and the minute hand is at 12, it means that it is 3 o'clock.Another type of clock that has gained popularity in recent years is the digital clock. It uses numbers to display the time instead of hands. Digital clocks are often found on electronic devices such as smartphones, computers, and microwaves. They provide a more precise and accurate representation of time, down to the exact second. For example, a digital clock might display 10:30:45, indicating that it is 10 hours, 30 minutes, and 45 seconds.Clocks have also evolved to include various features and functions. Some clocks have alarms, allowing us to set a specific time to wake up or be reminded of an important event. Others have timers and stopwatches, which come in handy for cooking or timing sports activities. There are even clocks that can automatically adjust to different time zones, making it easier for travelers to keep track of time when they are in a different country.中文回答：时钟是我们日常生活中必不可少的一部分。

The Role of Clocks in Our LivesClocks have always been an integral part of our lives, playing a crucial role in our daily activities and routines. They serve as a constant reminder of the passage of time, guiding us through our schedules and appointments. In the modern era, clocks have become even more sophisticated, offering a range of functions and features that make our lives easier and more convenient.Firstly, clocks help us to manage our time effectively. Whether it's waking up for school or work, attending meetings, or planning our daily tasks, clocks provide uswith a clear understanding of the time we have available.By setting alarms or reminders, we can ensure that we don't miss important deadlines or appointments. This ability to plan and organize our time effectively is crucial for success in both our personal and professional lives.Secondly, clocks are also a symbol of precision and accuracy. In the fields of science, engineering, and medicine, precise timing is essential for experiments, measurements, and procedures. Clocks with high-resolution timers and stopwatches are used to ensure that tasks arecompleted within the required timeframes. This precision is also crucial in sports, where timing is often the deciding factor in competitions.Moreover, clocks have also become a fashion statementin recent years. Designer watches and clocks are not only used to tell the time but also to complement our outfits and reflect our personalities. From sleek and modern designs to vintage and classic styles, clocks offer a range of options to suit every taste and occasion.However, the importance of clocks extends beyond their practical uses. They also have a cultural and historical significance. Clocks have been around for centuries, evolving from simple sundials and water clocks to the intricate mechanical and electronic clocks we have today. They are a testament to the advancement of technology and human ingenuity.In conclusion, clocks play a pivotal role in our lives, serving as both practical tools and cultural icons. They help us to manage our time effectively, ensure precision and accuracy, and reflect our personal styles. As technology continues to evolve, we can expect clocks tobecome even more sophisticated and integrated into ourdaily lives.**钟表在我们生活中的作用**钟表一直以来都是我们生活中不可或缺的一部分，在我们的日常活动和日常安排中扮演着至关重要的角色。

Dallas Semiconductor offers a variety of real time clocks (RTCs). The majority of these are available either as integrated circuits or modules. Modules include a real time clock integrated circuit, crystal, and lithium energy source encapsulated in one package.This application note is intended to help those customers who choose to use Dallas Semiconductor real time clock chips rather than modules and therefore need to attach their own crystal. The information contained in this article will be beneficial in maximizing accuracy and insuring proper operation of Dallas real time clocks by helping the customer to select the correct crystal to use and by providing a few basic guidelines that should be followed when placing the crystal on a PCB layout. This application note will also include an elementary discussion of the effect of temperature on the accuracy of real time clocks.This application note also includes a section on troubleshooting oscillator problems.CRYSTAL SELECTIONIn any crystal-based oscillator circuit, the oscillator frequency is based almost entirely on the characteristics of the crystal that is used. It is important to select a crystal that meets the design requirements. In particular, the specified load capacitance (C L ) is a critical crystal parameter that is often overlooked. This parameter specifies the capacitive load that must be placed across the crystal pins in order for the crystal to oscillate at its specified frequency. The crystal manufacturer actually “trims” the crystal to oscillate at its nominal frequency for the given specified load capacitance. Note that the C L is the capacitance that the crystal needs to “see” from the oscillator circuit, it is not the capacitance of the crystal itself.NOTE:Dallas Semiconductor RTC integrated circuits have on-chip bias stabilization networks and load capacitors which eliminate the need for external resistors or capacitors.As previously stated, the load capacitance that the crystal “sees” is due to the capacitance of the oscillator circuit itself. Any change in the load capacitance of the oscillator circuit will therefore have an affect on the frequency of that oscillator. Likewise, using a crystal that has a C L that is different than the actual load capacitance of the circuit will also affect the frequency of the oscillator.In general, using a crystal with a C L that is larger than the load capacitance of the oscillator circuit will cause the oscillator to run faster than the specified nominal frequency of the crystal. Conversely, using a crystal with a C L that is smaller than the load capacitance of the oscillator circuit will cause the oscillator to run slower than the specified nominal frequency of the crystal.The majority of Dallas Semiconductor RTCs have an internal capacitance of 6 pF across the crystal input pins. Recent RTC offerings from Dallas Semiconductor have 12.5 pF capacitance or are software configurable for 6 pF or 12.5 pF. For proper operation and accuracy, a crystal that meets the part's requirements should be used. As mentioned above, using a crystal with the wrong C L will cause the oscillator to run fast or slow. Limited characterization at Dallas Semiconductor has confirmed this. For example, limited characterization on the DS1485, which is designed for a 6 pF crystal, has revealed that the device will run approximately 4 minutes/month fast at room temperature (25°C) when a 12 pF crystal is used. The device has an accuracy within ±30 seconds/month when a 6 pF crystal is used.Application Note 58Crystal Considerations withSeveral vendors offer crystals that can be used with Dallas Semiconductor's real time clocks. These vendors include Epson and KDS/Daiwa. Equivalent crystals from other crystal manufacturers can also be used. As a reference, see Table 1 for recommended crystal characteristics.CRYSTAL SPECIFICATIONS Table 1PARAMETER SYMBOL MIN TYP MAX UNITS NOTES Nominal Frequency F032.768kHzLoad Capacitance C L6pF Temperature Turnover Point T0202530°CParabolic Curvature Constant k0.042ppm/°CQuality Factor Q40,00070,000Series Resistance R145kΩShunt Capacitance C0 1.1 1.8pF Capacitance Ratio C0/C1430600Drive Level D L1µWRTC CRYSTAL SUPPLIERSMANUFACTURER MODEL C L PACKAGE KDS/Daiwa Crystal Corp.DT-38DT-381DT-26S(1TB602G00)DT-261SDT-14DT-26S 32.768 Hz DMX-2632.768 kHz DS-VT-2006 pFCylinderCylinderCylinderCylinderCylinderCylinderCylinderCylinderEpson Crystal Corp.C-001RC-002RXC-002SH-32.768KAEC-002SH-32.768KAAC-004RC-005RMC-306MC-405MC-4066 pF, 12.5 pF6 pF, 12.5 pF6 pF12 pF 6 pF, 12.5 pF6 pF, 12.5 pF6 pF, 12.5 pF6 pF, 12.5 pF6 pF, 12.5 pFCylinderCylinderCylinderCylinderCylinderCylinderSMTSMTSMTHooray Electronics MMTF-32 6 pF Cylinder CRYSTAL LOAD COMPENSATIONDallas Semiconductor does not recommend using crystals that do not have a C L that matches the RTC's specification because this will decrease the accuracy of the clock. We find, however, that customers sometimes choose to use 12.5 pF crystals with our 6 pF RTCs. For this situation it is possible to improve the decreased accuracy caused by the C L mismatch. This can be accomplished by increasing the load capacitance that the crystal “sees” by connecting a capacitor in parallel with the crystal as shown in Figure 1. As a rule of thumb, the approximate capacitor value is equal to the specified load capacitance (C L) of the crystal minus 6 pF (the approximate load capacitance of the real time clock oscillator circuit). For example, if a 12 pF crystal is being used, a 6 pF capacitor should be placed in parallel with it to improve the accuracy of the oscillator. A 12 pF crystal is adjusted by the crystal manufacturer to oscillate at its specified nominal frequency when a 12 pF load is present. A 6 pF capacitor is therefore added to the 6 pF load of the oscillator circuit to compensate for the additional load that the crystal needs in order to oscillate at its specified nominal frequency.CRYSTAL CONFIGURATION WHEN 6 PF CRYSTAL IS NOT USED Figure 1As mentioned, a crystal with a C L of greater than 6 pF can be compensated with an external capacitor to improve the accuracy. However, it should be noted that the oscillator start-up time (the time it takes during initial power up for the oscillator to stabilize) will increase due to the increased capacitance in the feedback path of the oscillator. This capacitance decreases the loop gain of the oscillator, which in turn increases the start-up time. For example, limited characterization has shown that the start-up time for a 6 pF crystal is typically less than a couple hundred milliseconds, but can increase to one or two seconds when a 12 pF crystal with a 6 pF capacitor in parallel are used.NOISE AND CRYSTAL LAYOUT GUIDELINESSince the crystal inputs of the Dallas Semiconductor real time clocks have a very high impedance (about 109 ohms), the leads to the crystal act like very good antennae, coupling high frequency signals from the rest of the system. If a signal is coupled onto the crystal pins, it can either cancel out or add pulses. Since most of the signals on a board are much higher frequency than the 32.768 kHz crystal, it is more likely to add pulses where none are wanted. These noise pulses get counted as extra clock “ticks” and make the clock appear to run fast.It is very simple to determine if noise is the cause of the inaccuracy of a real time clock. The following steps illustrate how this can be done.1.Power the system up and synchronize the real time clock to a known accurate clock.2.Turn system power off.3.Wait for a period of time (two hours, 24 hours, etc.). The longer the time period, the easier it will beto measure the accuracy of the clock.4.Turn system on again, read clock, and compare to the known accurate clock.5.Re-synchronize the real time clock to the known accurate clock.6.Keep system powered up and wait for a period of time equal to the period in step 3.7.Read clock after waiting for the above period of time and compare to the known accurate clock.By using the above steps, the accuracy of the clock can be determined both when the system is powered up and when the system is powered down. If the clock proves to be inaccurate when the system is powered up, but is accurate when the system is powered down, the problem is most likely due to noise from other signals in the system. However, if the clock is inaccurate both when the system is powered up and when it is powered down, then the problem is not due to noise from the system.Since it is possible for noise to be coupled onto the crystal pins, care must be taken when placing the external crystal on a PCB layout. It is very important to follow a few basic layout guidelines concerning the placement of the crystal on the PCB layout to insure that extra clock “ticks” do not couple onto the crystal pins.1.It is important to place the crystal as close as possible to the X1 and X2 pins. Keeping the tracelengths between the crystal and the real time clock as small as possible reduces the probability of noise coupling by reducing the length of the “antennae.” Keeping the trace lengths small also decreases the amount of stray capacitance.2.Keep the crystal bond pads and trace width to the X1 and X2 pins as small as possible. The largerthese bond pads and traces are, the more likely it is that noise can couple from adjacent signals.3.If possible, place a guard ring (tied to ground) around the crystal. This helps to isolate the crystalfrom noise coupled from adjacent signals. See Figure 2 for an illustration of using a guard ring around a crystal.4.Try to insure that no signals on other PCB layers run directly below the crystal or below the traces tothe X1 and X2 pins. The more the crystal is isolated from other signals on the board, the less likely it is that noise will be coupled into the crystal. There should be a minimum of 0.200 inches between any digital signal and any trace connected to X1 or X2. The RTC should be isolated from any component that generates electromagnetic radiation (EMR). This is true for discrete and module type RTCs.5.It may also be helpful to place a local ground plane on the PCB layer immediately below the crystalguard ring. This helps to isolate the crystal from noise coupling from signals on other PCB layers.Note that the ground plane needs to be in the vicinity of the crystal only and not on the entire board.See Figure 2 for an illustration of a local ground plane. Note that the perimeter of the ground plane does not need to be larger than the outer perimeter of the guard ring.Note that care must be taken concerning the use of a local ground plane because of the stray capacitance that it introduces. This capacitance will be added to the crystal pins and if large enough could slow the clock down. Therefore, some factors must be taken into account when considering adding a local ground plane. For example, the capacitance due to the ground plane may be approximated byC = εA/twhereε = dielectric constant of the PCBA = area of the ground planet = thickness of the PCB layer.Therefore, to determine if a ground plane is appropriate for a given design, the above parameters must be taken into account to insure that the capacitance from the local ground plane is not sufficiently large enough to slow down the clock.EXAMPLE OF CRYSTAL PLACEMENT ON PCB Figure 2CLOCK ACCURACY OVER TEMPERATUREThe accuracy of a real time clock is directly dependent upon the frequency of the crystal. Therefore, since the resonant frequency of a crystal is dependent upon temperature, a real time clock will also be dependent upon temperature. The resonant frequency of a crystal is expressed in the following basic formula:f = f0 + k * (T - T0)2wheref0 = nominal frequencyk = parabolic curvature constantT0 =turnover temperatureT = temperatureThe values of the above parameters can be found in the data sheet of the crystal being used. The temperature characteristic of a nominal Daiwa crystal is illustrated in Figure 3, where f0 = 32.768 kHz, k = -0.042 ppm/°C, and T0 = 23°C. As can be seen in this figure, frequency has a parabolic relationship to temperature; as temperature deviates from the ideal 23°C, the crystal frequency becomes increasingly slower.Figure 4 shows the same basic curve; however, the Y axis has been changed to show the frequency deviation (in ppm) from the crystal’s nominal frequency at 23°C. This curve illustrates more clearly how the frequency of the crystal will affect the accuracy of the clock. A frequency deviation of 23 ppm translates into an accuracy of approximately ±1 minute per month. With this in mind, a quick glance at Figure 4 will give an approximate expected accuracy at a given temperature.The above information should help to provide a basic understanding of how temperature will affect Dallas Semiconductor real time clocks.CRYSTAL FREQUENCY VS. TEMPERATURE Figure 3FREQUENCY DEVIATION VS. TEMPERATURE Figure 4TROUBLESHOOTINGThis section is provided as a summary of the most frequent causes of real time clock inaccuracies. Most of these problems have been mentioned earlier, but are repeated here as a quick reference. This section has been divided into three parts. The first part will consider the factors that cause a real time clock to run too fast and the second part will consider the factors that cause a real time clock to run too slow. The third part deals with clocks that do not run.FAST CLOCKSThe following are the most common scenarios that cause a crystal-based real time clock to run fast.1.Noise coupling into the crystal from adjacent signals: This problem has been extensively coveredabove. Noise coupling will usually cause a real time clock to be grossly inaccurate.2.Wrong crystal: A real time clock will typically run fast if a crystal with a specified load capacitance(C L) greater than 6 pF is used. The severity of the inaccuracy is dependent on the value of the C L.For example using a crystal with a C L of 12 pF will cause the real time clock to be about 3-4 minutes per month fast.SLOW CLOCKSThe following are the most common scenarios that cause a crystal-based real time clock to run slow.1.Overshoot on real time clock input pins: It is possible to cause a real time clock to run slow byperiodically stopping the oscillator. This can be inadvertently accomplished by noisy input signals to the real time clock. If an input signal rises to a voltage that is greater than a diode drop (~0.3V) above V DD, the ESD protection diode for the input pin will forward bias, allowing the substrate to be flooded with current. This, in turn, will stop the oscillator until the input signal voltage decreases to below a diode drop above V DD.This mechanism can cause the oscillator to stop frequently if input signals are noisy. Therefore, care should be taken to insure that there is no overshoot on input signals.Another situation that is common to overshoot problem is having an input to the real time clock at5 volt when the real time clock is in battery back-up mode. This can be a problem in systems thatsystematically shut down certain circuits, but keep others powered up. It is very important to insure that there are no input signals to the real time clock that are greater than the battery voltage when the device is in battery back-up mode.2.Wrong crystal: A real time clock will typically run slow if a crystal with a specified load capacitance(C L) less than 6 pF is used. The severity of the inaccuracy is dependent on the value of the C L.3.Stray capacitance: Stray capacitance between the crystal pins can slow a real time clock down.Therefore care must be taken when designing the PCB layout to insure that the stray capacitance is kept to a minimum.4.Temperature: The further the operating temperature is from the crystal turnover temperature, theslower the crystal will oscillate. See Figures 3 and 4.Clock Does Not RunThe following are the most common scenarios that cause a crystal-based real time clock not run.1.The single most common problem when the clock does not run is that the CH (clock halt) or EOSC(enable oscillator) bit has not been set or cleared, as required. Many Dallas Semiconductor RTCs include a circuit that will keep the oscillator from running when power is first applied. This allows a system to wait for shipment to the customer, without drawing power from the backup battery. When the system is powered for the first time, the software/firmware must enable the oscillator and prompt the user for the correct time and date.2.Parasitic loads caused by condensation, incomplete solder flux removal or other loads can keep theoscillator from running.3.Floating supply pins. Many Dallas RTCs have multiple supply inputs. Any unused input, such asVbat, must be grounded. If a supply pin is left floating, communication with the RTC may not work. Surface mount crystals may have some N/C (no connect) pins. Make sure that the correct pins from the crystal are connected to the X1 and X2 pins. Note that the oscillator circuit on Dallas RTCs are low power; and the signal at the oscillator input pins may be only a few hundred millivolts peak to peakREFERENCES1.Eaton, S. S. Timekeeping Advances Through COS/MOS Technology, RCA Application NoteICAN-6086.2.Eaton, S. S. Micropower Crystal-Controlled Oscillator Design Using RCA COS/MOS Inverters,RCA Application Note ICAN-6539.3.Meyer, R. G. “MOS Crystal Oscillator Design,” IEEE Journal of Solid-State Circuits, Vol. SC-15,No. 2, pp. 222-227, April 1980.4.Williamson, T. Oscillators for Microcontrollers, Intel Application Note AP-155.。

闹钟的用处英语作文Title: The Significance of Alarm Clocks。

Alarm clocks play a pivotal role in our daily lives, serving as indispensable tools to wake us up promptly, ensuring we start our days on time and stay organized.Their utility extends far beyond merely waking us up; they are instrumental in maintaining our schedules, enhancing productivity, and even improving our overall well-being.First and foremost, alarm clocks serve the fundamental purpose of waking us up in the morning. In today's fast-paced world, where time is of the essence, oversleeping can lead to a cascade of consequences, from tardiness to missed appointments or deadlines. Alarm clocks provide a reliable mechanism to rouse us from our slumber at the designated time, allowing us to begin our day promptly and efficiently.Moreover, alarm clocks help instill discipline and routine in our lives. By adhering to a consistent wakingtime set by the alarm, we establish a structured daily schedule. This regularity promotes productivity and time management skills, enabling us to allocate our time effectively to various tasks and responsibilitiesthroughout the day.Furthermore, alarm clocks contribute to our mentalwell-being by reducing stress and anxiety associated with oversleeping or being late. Waking up to the sound of an alarm provides a gentle transition from sleep to wakefulness, allowing us to start our day feeling refreshed and prepared. This sense of readiness fosters a positive mindset, setting the tone for a productive and fulfilling day ahead.In addition to their role in waking us up, alarm clocks serve as reminders for important events or activities throughout the day. Many modern alarm clocks feature customizable settings, allowing users to set multiplealarms for various purposes, such as appointments, meetings, or medication reminders. These timely reminders help usstay organized and on track, preventing the risk offorgetting essential tasks or commitments.Alarm clocks also play a significant role in promoting healthy sleep habits and sleep hygiene. By setting a consistent waking time, we synchronize our internal body clocks, also known as circadian rhythms, with external cues such as light and darkness. This consistency reinforces our body's natural sleep-wake cycle, improving the quality and duration of our sleep over time. Additionally, the act of setting an alarm encourages us to establish a regular bedtime routine, further enhancing our sleep quality.Moreover, alarm clocks can be tailored to suit individual preferences and lifestyles, with a wide range of features and designs available to cater to diverse needs. From traditional analog clocks to digital clocks with advanced functionalities such as sunrise simulation or customizable alarm tones, there is an alarm clock to suit every preference and budget. This versatility ensures that everyone can find an alarm clock that meets their specific requirements, enhancing its effectiveness and usability.In conclusion, alarm clocks serve a multitude of purposes beyond simply waking us up in the morning. They help maintain discipline and routine in our lives, reduce stress and anxiety, improve productivity, and promote healthy sleep habits. By incorporating an alarm clock into our daily routines, we can reap the benefits of a more organized, efficient, and fulfilling lifestyle.。

关于时钟的作文英文Title: The Significance of Timekeeping: An Essay on Clocks。

Time is the essence of life, an intangible force that governs our existence. At the heart of this intricate dance lies the humble yet indispensable invention the clock. From ancient sundials to modern atomic clocks, the evolution of timekeeping instruments mirrors the progress of human civilization itself.Clocks serve as more than mere tools for telling time; they are symbols of precision, discipline, and order. In a world governed by schedules and deadlines, clocks act as silent sentinels, guiding us through the passage of time. They dictate the rhythm of our lives, from the moment we wake until we retire to sleep.The importance of accurate timekeeping cannot be overstated. In fields such as astronomy, navigation, andindustry, precise measurements of time are paramount. Without synchronized clocks, the coordination of global activities would be impossible, leading to chaos and inefficiency. Imagine trains running late, flights missing their schedules, or financial transactions occurring out of sync. The consequences would be dire.Moreover, clocks serve as reminders of our mortality. The relentless march of time, marked by the steady tick-tock of a clock, reminds us of the fleeting nature of life. Each passing second is a reminder to cherish the moments we have and make the most of our time on this planet.Beyond their practical utility, clocks also hold cultural and artistic significance. Throughout history, clocks have been adorned with intricate designs, reflecting the aesthetic tastes of their time. From the ornate craftsmanship of medieval clocks to the sleek modern designs of today, clocks serve as expressions of human creativity and ingenuity.Furthermore, clocks play a crucial role in thedevelopment of society. The standardization of time brought about by the proliferation of clocks enabled the coordination of activities on a global scale. Itfacilitated the rise of industrialization, the expansion of trade networks, and the emergence of modern institutions. In essence, clocks served as the foundation upon which modern society was built.Yet, despite their ubiquity, clocks are often taken for granted. In our fast-paced world, where time is of the essence, we rarely pause to appreciate the marvel of precision engineering that lies within each timepiece. We glance at our watches or smartphones without a second thought, oblivious to the centuries of innovation that have led to their creation.In conclusion, clocks are more than mere instrumentsfor telling time; they are symbols of human progress, ingenuity, and civilization. They serve as reminders of our mortality, the importance of precision, and the interconnectedness of our global society. As we navigate the complexities of the modern world, let us not forget thehumble clock and the profound role it plays in shaping our lives.。

A clock is a timeless invention that has been an integral part of human life for centuries.It is a device used to measure,keep,and indicate time.The history of clocks dates back to ancient civilizations,but it was the invention of the mechanical clock in the 14th century that truly revolutionized timekeeping.The Evolution of ClocksThe earliest forms of timekeeping were the sun dials,which relied on the position of the sun to tell time.However,these were limited by weather conditions and the lack of light at night.The invention of water clocks,or clepsydras,in ancient Egypt and China was a significant advancement,as they could measure time in the absence of sunlight.The mechanical clock,with a verge escapement mechanism,was invented in Europe around1300.This allowed for a more consistent and accurate timekeeping mechanism, independent of environmental factors.The introduction of the pendulum to the clock mechanism in1656by Christiaan Huygens greatly increased the accuracy of timekeeping devices.Types of ClocksThere are various types of clocks,each serving different purposes and operating on different principles:1.Wall Clocks:These are typically found in homes and offices,displaying the time on a dial with hour,minute,and sometimes second hands.2.Pocket Watches:Once a symbol of status and elegance,pocket watches are now more of a collectible item,with a cover that opens to reveal the time.3.Cuckoo Clocks:Originating from the Black Forest in Germany,these clocks are known for their mechanical birds that cuckoo on the hour.4.Grandfather Clocks:Also known as longcase clocks,these tall,freestanding clocks are driven by a pendulum and chime on the hour.5.Digital Clocks:These modern clocks display time in a digital format,often with additional features like alarms and temperature readings.6.Atomic Clocks:The most accurate timekeeping devices,atomic clocks use the vibrations of atoms to measure time,accurate to within a second over millions of years.Importance of ClocksClocks are not just for telling time they have played a significant role in shaping human society.They have influenced the way we work,with the advent of factory work and the 9to5schedule.They have also impacted our social lives,dictating when we eat,sleep, and engage in various activities.In addition,clocks have been a source of inspiration for art,literature,and philosophy, often symbolizing the passage of time and the fleeting nature of life.Modern InnovationsWith the advent of technology,clocks have become more than just timekeepers. Smartwatches,for example,integrate with smartphones to provide notifications,fitness tracking,and even the ability to make payments.ConclusionThe clock,in its various forms,has been a fundamental part of human life,shaping our routines,our understanding of time,and even our cultural expressions.As technology advances,the way we interact with timekeeping devices continues to evolve,but the essence of what a clock representskeeping track of our precious momentsremains unchanged.。

clock 反向时钟约束英文回答：Clocks are an essential part of our daily lives, helping us stay organized and on schedule. However, what if we had a reverse clock? A clock that counts down instead of up, turning time on its head. This concept may seem strange at first, but let's explore the possibilities and constraints of a reverse clock.Firstly, a reverse clock would change the way we perceive time. Instead of counting the hours and minutes that have passed, we would be counting down the time remaining. For example, if it's currently 3 PM, a reverse clock would display 9 hours remaining until midnight. This shift in perspective could have both positive and negative effects.On the positive side, a reverse clock could potentially make us more mindful of our time. Knowing exactly how muchtime we have left until a deadline or an event could help us prioritize tasks and manage our time more efficiently.It could serve as a constant reminder that time is limited and encourage us to make the most of each moment.On the other hand, a reverse clock could also create additional pressure and anxiety. Seeing the time ticking away could make us feel like we're running out of time, even if we still have plenty left. This could lead to unnecessary stress and a constant feeling of urgency.In terms of practicality, a reverse clock would require a significant shift in our current timekeeping systems. We would need to reprogram our devices, watches, and clocks to display time in reverse. This could be a complex and time-consuming process, requiring updates and adjustments to various software and hardware.Additionally, a reverse clock would also affect our daily routines and schedules. For example, if we typically wake up at 7 AM, a reverse clock would indicate that we have 17 hours until our desired wake-up time. This couldpotentially disrupt our sleep patterns and make it challenging to plan activities with others who still follow the traditional forward clock.Despite the challenges and potential drawbacks, a reverse clock could also bring some interesting possibilities. For example, it could be a fun and unique way to challenge ourselves in time-sensitive activities, such as races or games. It could add an element of excitement and unpredictability, as we try to beat the clock counting down.中文回答：时钟是我们日常生活中必不可少的一部分，帮助我们保持组织和按时完成任务。