The minimum system of single chip microcomputer, or the minimum application system, refers to the system in which the single chip microcomputer can work with the least components.
For 51 series single chip microcomputer, the minimum system should generally include: single chip microcomputer, crystal oscillator circuit and reset circuit. The following is a minimum system circuit diagram of 51 single chip microcomputer.
explain
Reset circuit: it is composed of capacitor series resistance. According to the figure and the property of "capacitor voltage cannot change suddenly", when the system is powered on, the rst pin will have a high level, and the duration of this high level is determined by the RC value of the circuit. The typical 51 single chip microcomputer will reset when the high level of RST pin lasts for more than two machine cycles. Therefore, the reliable reset can be guaranteed by properly combining the value of RC. General textbooks recommend that C take 10u and r take 8.2k. Of course, there are other methods. The principle is to make the RC combination produce a high level of no less than 2 machine cycles on the rst pin. As for how to calculate quantitatively, you can refer to books related to circuit analysis.
Crystal oscillator circuit: the typical crystal oscillator is 11.0592Mhz (because 9600 baud rate and 19200 baud rate can be obtained accurately, which is used for occasions with serial communication) / 12Mhz (to generate accurate US level time interval, which is convenient for timing operation)
Single chip microcomputer: one AT89S51 / 52 or other 51 series compatible single chip microcomputer
Special note: for pin 31 (EA / VPP), when the high level is connected, the MCU starts from 0000H of the internal ROM after reset; When the low level is connected, the reset is directly executed from the 0000H of the external ROM. This is easy for beginners to ignore.
Reset circuit
MCU reset circuit is like the restart part of the computer. When the computer crashes in use, press the restart button, and the program inside the computer will be executed from scratch. Single chip microcomputer is the same. When the single chip microcomputer system is running and the program flies due to environmental interference, press the reset button and the internal program will be executed automatically from the beginning.
The reset circuit of single chip microcomputer is shown as follows:
It is introduced in the book that 51 single chip microcomputer can be reset only by connecting a high level at pin 9 for 2us. How is this process realized?
In the single chip microcomputer system, the system resets once when it is powered on and started. When the key is pressed, the system resets again. If it is pressed again after release, the system will reset. Therefore, the reset can be controlled in the running system through the opening and closing of the key.
Why is it reset when starting up
In the circuit diagram, the capacitance is 10uF and the resistance is 10K. Therefore, according to the formula, it can be calculated that the time required for the capacitor to charge to 0.7 times the power supply voltage (the power supply of the single chip microcomputer is 5V, so charging to 0.7 times is 3.5V) is 10K * 10uF = 0.1s.
In other words, within 0.1s of computer startup, the voltage at both ends of the capacitor increases at 0 3.5V. At this time, the voltage at both ends of 10K resistor decreases from 5 1.5V (the sum of the voltages at all parts of the series circuit is the total voltage). Therefore, within 0.1s, the voltage received by RST pin is 5V 1.5V. In 51 single chip microcomputer with 5V working normally, the voltage signal less than 1.5V is a low-level signal, while the voltage signal greater than 1.5V is a high-level signal. Therefore, the MCU system will reset automatically within 0.1s after startup (the time of high-level signal received by RST pin is about 0.1s).
Why does it reset when the key is pressed
After the MCU is started for 0.1s, the voltage at both ends of capacitor C is continuously charged to 5V. At this time, the voltage at both ends of 10K resistor is close to 0V, and RST is at low level, so the system works normally. When the key is pressed, the switch is turned on. At this time, a circuit is formed at both ends of the capacitor, and the capacitor is short circuited. Therefore, in the process of pressing the key, the capacitor begins to release the charge before charging. Over time, the voltage of the capacitor changes from 5V to 1.5V or even less within 0.1s. According to the series circuit voltage is the sum of all parts, at this time, the voltage at both ends of 10K resistor is 3.5V or even greater, so RST pin receives high level again. The single chip microcomputer system automatically resets.
Summary
1. The principle of the reset circuit is that the rst pin of the single chip microcomputer receives a level signal above 2us. As long as the charge and discharge time of the capacitor is greater than 2us, the reset can be realized, so the capacitance value in the circuit can be changed.
2. Press the key to reset the system, which is caused by the capacitor in a short circuit circuit, releasing all electric energy and increasing the voltage at both ends of the resistance.
Introduction of minimum system circuit of 51 single chip microcomputer
1.51 the polarity capacitance C1 of the minimum system reset circuit of single chip microcomputer directly affects the reset time of single chip microcomputer. Generally, 10 30uf is used. The larger the minimum system capacitance of 51 single chip microcomputer is, the shorter the reset time is required.
2.51 the minimum system crystal oscillator Y1 of single chip microcomputer can also use 6mhz or 11.0592Mhz. Under normal working conditions, the crystal oscillator with higher frequency can be used. The oscillation frequency of the minimum system crystal oscillator of 51 single chip microcomputer directly affects the processing speed of single chip microcomputer. The greater the frequency, the faster the processing speed.
3.51 the minimum system starting capacitance C2 and C3 of single chip microcomputer are generally 15 33pf, and the closer the capacitance is to the crystal oscillator, the better the crystal oscillator is to the single chip microcomputer. Port P0 is an open drain output. When it is used as the output port, a pull resistance needs to be added, and the resistance value is generally 10K.
When the timer mode is set, adding 1 counter counts the internal machine cycles (one machine cycle is equal to 12 oscillation cycles, that is, the counting frequency is 1 / 12 of the crystal oscillation frequency). The count value n multiplied by the machine cycle tcy is the timing time t.
When set to counter mode, the external event count pulse is input to the counter by t0 or T1 pin. The t0 and T1 pin levels are sampled during s5p2 of each machine cycle. When a high level input is sampled in one cycle and a low level is sampled in the next cycle, the counter is incremented by 1, and the updated count value is loaded into the counter during s3p1 of the next machine cycle. Since it takes 2 machine cycles to detect a falling edge from 1 to 0, the sampled level is required to maintain at least one machine cycle. When the crystal oscillator frequency is 12Mhz, the maximum counting frequency shall not exceed 1 / 2MHz, that is, the period of counting pulse shall be greater than 2ms.

Anyone know whats wrong with my computer mouse?


are you using a wireless mouse? time to change the batteries. or are you using an infra red mouse? your desk is now shiny and the IR beam is bouncing around on it. put something non-glossy under it like a sheet of plain paper. try again or are you using a rollerball mouse? take the ball out and clean it, clean the bits that the ball rubs against inside the hole the ball goes in.
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Will a computer mouse work if it has been dropped in the water?
Yes, it depends since they are in plastic cases but leave it out for a week and it should work.. You may need to blow dry it abit because sometimes the water may not be able to escape very well. Nothing will happen bad if it has water anyway, it will just not work.


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what's inside of a computer mouse?
not cheese
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Where can I find a computer mouse which is silent?
the microswitches in a mouse make the clicking noise - i do not know of a microswitch with a silent action. if there is a mouse out there that uses pressure switches rather than microswitches then that would be quieter but the mouse would be of very poor quality. surely the noise of the keyboard is far louder than the mouse? i think you should either 1.re arrange the sitting room in order to be further away from the pc 2.turn the tv up 3.wear ear plugs or- 4. see a doctor about the state of your nerves!
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Is the computer mouse about to go extinct?
The Evolution of the MousenWe did some digging on the history of the computer mouse. It's perhaps technology's most innovative tool, matched with the most peculiar name. The mouse was invented in 1964 by Douglas Engelbart. The original was comprised of two metal wheels sending signal to a circuit board cased up in a wooden box. The invention was called the "mouse" because of its literal resemblance to our small furry friends.
Check out this video of Engelbart demonstrating the computer mouse for the first time in 1968. Since then, the more functional trackball mouse was brought to us in 1972 by Bill English, and the modern day optical mouse was delivered in 1980. Improvements have been made for optimal computer screen navigation since then, but is there a next step in computer mouse evolution? Has it met its end?The End of the MousenStatistically, there's a 15% chance that you accessed this blog post using a touchscreen / not using a mouse. This number is steadily rising as tablets, smartphones, touchscreen mp3 players, and touchscreen computers are becoming more prominent in the technology market. After all, is not it easier to simply touch where you want to navigate on a screen rather than coordinating through a separate device?A perfect application of touchscreen technology is Internet browsing. If you come across a picture icon that you want to enhance, just touch it. If you want to go back to a page that you were just on, just touch the back arrow, or touch and swipe your finger backward. You can easily navigate through text boxes by simply touching them to place your cursor.
Word processing is just as easy to navigate without a computer mouse. You can use your finger to highlight text, place your cursor, make font edits, copy and paste, and do literally everything that you can do with a mouse. Navigating through your operating system is just as simple as web browsing and word processing. Simply touch the programs and menus that you want to open. It does not get much more intuitive than that.
Without a doubt, technological products are advancing in this direction of extreme intuition using touchscreen technology. As more tablets, smartphones, and touchscreen computers enter the market, more people will pick them up and discover the extreme ease of navigating your computer's software without a computer mouse. Over time, technology producers will continue to wean us off of our use of the mouse and move us toward touchscreen technology until the majority of us see no need to pair a computer mouse with our devices. Touchscreens will most likely get larger and less cluttered to allow for easier navigation with our fingertips, and more "gesture control" technology will be introduced to even surpass the need to touch the screen for some applications. The sky's the limit with new technology, and we will all be just as giddy about these new possibilities as Engelbart was about his wooden mouse.
Imagine: A Workday without a MousenAre you nervous about the potential of losing your computer mouse? For some of you, it may seem as though you've just now become accustomed to using it (but hopefully not). Rest assured, there will always be an option to use a mouse with your computer, even though it's function will become superfluous. Think of it like watching movies via video cassette. The option is still available to purchase cassette players and hook them into televisions, but the latest movies will not be released on that format. Is the computer mouse about to go extinct?.

How do you lock your computer keyboard?


I would start the laptop in nontoxic mode and see if it does the identical element (press F8 while the laptop is establishing up). If it does it sort of feels like a hardware difficulty of a couple of variety. If its a pc I would verify out plugging a different keyboard into it and see must you get the identical element. If its a pc you might also ought to identify the enterprise and have it transformed
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I am currently re-formatting my custom-built computer. Keyboard does not work?
You are constructing a splendid laptop. Excellent choice of constituents. You cannot cross fallacious with Zalman merchandise. Top manufacturer fine names to your add-ons. Cooling process turns out nice, however for the heck of it upload 120mm and 80mm case enthusiasts. Do you wish to have two HDMI ports at the picture card? If now not, you option is pleasant. Great at the outside TV tuner. You did not point out track, or did you? Make definite your entire drivers and application are possible with Vista sixty four. And duvet your self with a few backup. Perhaps an outside case and force equal, or greater, then your case force and select up a replica of Paragon-Software's Drive reproduction. A screaming desktop. Have amusing!


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Who decided where the keys on a computer keyboard would be? and Why did they decide the way they did?
They used to have them in alphabetical order but apparently, when people were doing typewriting work, they were doing it too quickly so they mixed the letters on the keyboard up to make it more complicated and difficult! It's been like this since. We call it the qwerty keyboard because those are the first letters on the keyboard! qwerty!
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What's a good way to clean a computer keyboard?
A guy at work put his in the dishwasher, and surprisingly it doesnt work now :) water can get inbetween keys and damage the circuits that connect the keys best way to clean is a damp cloth and i use damp cotton buds to get inbetween the keys.
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What could cause the alphabets on a computer keyboard to show up as numbers?
Your keyboard has been infected by the computer gremlins. You can never use the computer again. Throw it away
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How do you clean a computer keyboard?
there is a keyboard cleaner which you can buy from many stores: Staples, Office Depot etc. They go by the generic names of Keyboard Antistatic cleaner. Do not cost that much and many people have them (under $15.00) for the most part.
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How do you clean out a computer keyboard?
I use Q-tips
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How do you get a computer keyboard to work on a PS2?
Hi. Something is mistaken. You have the keyboard and mouse mounted accurately. Try the KVM on a further laptop or transfer the keyboard and mouse cables. If the concern persists (with the keyboard now not operating at the moment laptop) then it feels like a faulty KVM.
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How often do you clean your computer keyboard?
Oh, every 2-3 years, I would guess
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How can I clean my computer keyboard?
Use a powerful vacuum cleaner.USB vacuum cleaners are also available. They do a nice job.
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How much does the average computer keyboard cost?
An average computer keyboard costs 5$ to 10$. But some of the specialized keyboard price are like are this : original Logitech Value 100 Wired Keyboard(SMQ3005) US$ 12.35 Samsung PKB-7000 Crystal Multimedia Keyboard US$ 36.76 Samsung PKB-8100 Multimedia Calculator keyboard US$ 50.99 Samsung PKB-8000 Zen Keyboard US$ 26.99 Samsung PKB-5400 Stylish Slim Keyboard US$ 28.99 Samsung PLEOMAX PKB-5000 Slim Touch Multimedia Keyboard US$ 27.99 Samsung PKB-4500 Slim Keyboard US$ 25.99 Samsung PKB-3000 Multimedia Keyboard US$ 23.24 Samsung PKB-3600 wired Multimedia Keyboard US$ 26.99 Samsung Authenic Keyboard QSENN DT-35 Black/White US$ 29.99
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Why does my desktop computer keyboard randomly stop working?
Replace the keyboard. It is not worth the hassle to try and find out
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What made the person who invented the computer keyboard arrange the alphabet in the order that it is?
This Site Might Help You. RE: What made the person who invented the computer keyboard arrange the alphabet in the order that it is? Why isn't QWERT- ABCDE??? Why are the letters all mixed up? Was or Is there a special purpose for this?

Why are computer keyboard keys printed in Uppercase? [duplicate]


I believe it's partly alexeypegov's answer of distinctiveness, but also historical reasons. The first typewriters, which also had the first QWERTY keyboard, only supported upper case letters
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What combination of Keys on the Computer Keyboard make a musical note symbol?
Turn on your number lock and still use your keypad. With number lock off they can act as navigation hot-keys as you saw. I use alt codes on a daily basis and am irritated when I accidentally turn it off. I am entering the alt code such as 0176 for and my browser thinks I am talking to it. According to your results you are using the number pad. It just needs to get turned on. You can usually set number lock on through your BIOS. This will turn it on automatically when Windows starts. Pressing delete or F1 lets you into your BIOS,


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What's the best way to clean a computer keyboard?
pop each key out, then use a paint brush to dust the base. use an all purpose cleaner to clean each key. do not open the whole keyboard as it will be difficult to put it back together if this is your first time to do it.
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Who decided where the keys on a computer keyboard would be? and Why did they decide the way they did?
They used to have them in alphabetical order but apparently, when people were doing typewriting work, they were doing it too quickly so they mixed the letters on the keyboard up to make it more complicated and difficult! It's been like this since. We call it the qwerty keyboard because those are the first letters on the keyboard! qwerty!
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computer keyboard questions, which is best?
I have a Logitech G15 Refresh Keyboard. I would and always highly recommend it. It retails at a very good price, I paid $130 NZD for it and had well been worth the money. I would reccommend and keyboard from the Logitech G series. Have a quick look at their website. (Post link below)
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how to remove the dust from your computer keyboard safely with out chemicals?
Two ways: 1) vacuum the dust out with one of those small brushes that come with vacuum cleaners, or 2) buy a can of compressed air cleaner at a computer store, blow out the keyboard, and THEN, vacuum the dust out with one of those small brushes that come with vacuum cleaners. Works every time
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What is the best household way to clean my computer keyboard?
hoover it with the machine off
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What is a good way to clean my computer keyboard?
Get a mini-vaccum cleaner from any computer peripheral shop and you can use it to clean computer and other similar equipment., including HiFi, speakers etc
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can i use a computer keyboard and mouse on a PS3?
So long as it has a USB connection (as you said), it should work. This goes for both keyboards and mice
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How do you clean a computer keyboard?
there is a keyboard cleaner which you can buy from many stores: Staples, Office Depot etc. They go by the generic names of Keyboard Antistatic cleaner. Do not cost that much and many people have them (under $15.00) for the most part.
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Is it true that you can clean a computer keyboard in the dishwasher. If yes, how?
I would not recommend putting it in a dishwasher unless you dis assemble it first and remove all electrical items the water would get trapped inside of it and will take a very long time to dry out
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My computer keyboard isnt typing the correct symbols?
The Alt-key shortcut is Alt3
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change my computer keyboard system?
Go to "Control Panel" -> "Regional and Language Options" -> Choose tab of "Languages" --> Click "Details" --> Click "Add" and select "English UK" language and keyboard layout as "US" and click "OK", in the drop down menu select the recently added setting and click "OK" to finish!
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What's the best way to clean a desktop PC computer keyboard?
dishwasher. really. not an old one though as they are made differently
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what is the best saved way to clean your computer keyboard ?
'Jay' is right on. I do mine in the sink with lots of soap and hot water. Make sure you rinse it well to get the soap and water out. Stand it on end somewhere overnight so that it will dry. I learned about this during a college course on computer maintenance and it works and wo not damage the keyboard

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The mobile phone feel of this keyboard is very good. I switched to this keyboard directly from the film-like mechanical-feel keyboard. I didn’t feel uncomfortable at all, and I got started very quickly.



My main need is typing and typing codes. I think the feel of this keyboard is really good, and there are very few mistakes.



The sound of the keyboard is also much quieter than I imagined, and it hardly disturbs others. When I usually type, I tap so hard that my girlfriend can't stand it anymore, so I bought this keyboard for me. The current one will not disturb her at all, and the pleasure of typing is still the same as before, even smoother than before. The fly in the ointment is that the sound of the backspace key is slightly louder than the other keys.



However, the seller's service is very good. I took a video, and he showed it to them after the sale, and told me that this is normal. In fact, I am a bit harsh. The sound of the backspace key is completely acceptable to me, but it is different from other keys, and it feels a bit awkward.