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| − | [http://zelankom.iespana.es/la-casa/ la casa nella prateria] [http://glmillig.angelfire.com/library/norther.htm norther] [http://grizs.iespana.es/articles/ww-hotmail.htm ww hotmail com] [http://masteriii.isuisse.com/kansas-city.htm kansas city massacre] [http://borg77.iespana.es/styles/i-am/ i am a woman in love mp3] [http://night-sacrifice.isuisse.com/resources/www-tamagochi.htm www tamagochi giochi com] [http://marebeck.angelfire.com/new/s-g/ s g pubblicita] [http://blaleyne.angelfire.com/new/in-fondo.htm in fondo al cuore] [http://zelankom.iespana.es/vacanza-barche/ vacanza barche vela grecia] [http://farshad-uk.isuisse.com/styles/indirizzo-email.htm indirizzo email] [http://miki-hana.isuisse.com/description/viaggi-eritrea/ viaggi eritrea] [http://marebeck.angelfire.com/new/nuova-audi/ nuova audi a2 auto nuove] [http://pahopewe.angelfire.com/resources/dolanes.htm dolanes] [http://flameshes.isuisse.com/topic/car-audio/ car audio jvc] 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[http://annie-fialochka.ibelgique.com/lib/giochi-tutti.htm giochi tutti] [http://magenta4eva.iespana.es/loewe-.htm loewe 6222 xemix] [http://farshad-uk.isuisse.com/styles/ethan-frome.htm ethan frome] [http://night-sacrifice.isuisse.com/resources/www-oralsex.htm www oralsex com] [http://borg77.iespana.es/styles/ricerche-su/ ricerche su squali] [http://therealocelot.ibelgique.com/articles/ragazzo-ortisei/ ragazzo ortisei] [http://cutterjon.isuisse.com/content/la-collina.htm la collina dei conigli] [http://girlwithacurl.ibelgique.com/small/caricaturas-gratis.htm caricaturas gratis porno] [http://brkim.angelfire.com/resources/mappa-metro.htm mappa metro milano] [http://hexa1598.ibelgique.com/femrat/ femrat] [http://ofdays.isuisse.com/library/deha/ deha] [http://hexa1598.ibelgique.com/kylie-minogue/ kylie minogue slow chemical brothers] [http://dreameradrift.ibelgique.com/small/i-cento/ i cento passi libri] [http://abr-abrante.iespana.es/content/haakon-i/ haakon i] [http://zelankom.iespana.es/generali-assicurazioni/ generali assicurazioni] [http://zelankom.iespana.es/oggetti-smarriti/ oggetti smarriti] [http://ruoj-ruoj.isuisse.com/description/mp-yeah/ mp3 yeah] [http://therealocelot.ibelgique.com/articles/bad-day/ bad day] [http://pahopewe.angelfire.com/resources/mappa-tunisia.htm mappa tunisia] [http://glmillig.angelfire.com/library/phanton.htm phanton] [http://the-ile.iespana.es/batterie-nokia/ batterie nokia 6680] [http://glmillig.angelfire.com/library/zen-creative.htm zen creative 40gb] [http://mubathsh.angelfire.com/text/reti-sud.htm reti sud] [http://stdamin.angelfire.com/resources/ferr.htm ferr] [http://songsoutofkey.isuisse.com/view/yashica.htm yashica 70] [http://mongo42.ibelgique.com/biglietti-falsi/ biglietti falsi vasco] [http://zelankom.iespana.es/direccion/ direccion] [http://callie-avalon.iespana.es/nuova-bmw/ nuova bmw 120d diesel auto nuove] The vast majority of electronic systems operate at some fixed frequency.
| + | The vast majority of electronic systems operate at some fixed frequency. |
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| | Usually the component that fixes that frequency is a quartz crystal, sealed in a metal can. | | Usually the component that fixes that frequency is a quartz crystal, sealed in a metal can. |
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| | Unfortunately, many people confuse the "clock signal" generated by an oscillator (a simple metronome beat, tone, at constant frequency) with far more complicated "clock system"s that keep track of seconds, minutes, hours, and sometimes days, weeks, months, and years. | | Unfortunately, many people confuse the "clock signal" generated by an oscillator (a simple metronome beat, tone, at constant frequency) with far more complicated "clock system"s that keep track of seconds, minutes, hours, and sometimes days, weeks, months, and years. |
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| − | == for further readin | + | == for further reading == |
| − | 1000
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| − | g ==
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| | * [http://techref.massmind.org/techref/clocks.htm massmind: clocks] | | * [http://techref.massmind.org/techref/clocks.htm massmind: clocks] |
| | * [http://en.wikipedia.org/wiki/Crystal_oscillator Wikipedia: crystal oscillator] | | * [http://en.wikipedia.org/wiki/Crystal_oscillator Wikipedia: crystal oscillator] |
| − | * [http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE | + | * [http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en021190 "App Note AN949: Making Your Oscillator Work" by Brett Duane] |
| | + | * [http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en020706 "App Note AN943: Practical PICmicro® Oscillator Analysis and Design" by Ruan Lourens] |
| | + | |
| | + | [[Category:Components]] |
Revision as of 13:12, 9 September 2007
The vast majority of electronic systems operate at some fixed frequency.
Usually the component that fixes that frequency is a quartz crystal, sealed in a metal can.
(Some very-low-cost devices might use a "ceramic resonator" (made of high-stability piezoelectric ceramics, generally lead zirconium titanate)or a resistor and a capacitor to fix the frequency).
The entire circuit that generates the frequency is called an "oscillator", includes the resonant part (crystal, resonator, or RC), some capacitors, and a silicon chip and therefore is called a hybrid device.
(An oscillator that uses a resistor and a capacitor to fix the frequency is called a "RC oscillator".
An oscillator that uses a crystal to fix the frequency is called a "crystal oscillator".)
The oscillator includes, in addition to the frequency-fixing component just mentioned, an amplifier and capacitors.
Oscillators usually come in a metal can, but Epson also encapsulates them in plastic. Typically an oscillator can has 4 pins. Inside the can is all the components of the oscillator. One applies DC power on 2 of the pins, and the oscillating signal (the "CLK OUT") appears on another pin. (The remaining pin is unused).
An oscillator can also be made from scratch using crystal in a (2-pin) metal can, a couple of capacitors, an resitor and an inverter.
In either case, the frequency is printed on the top of the crystal or oscillator.
Many microcontrollers have 2 pins (typically labeled "XTAL1" and "XTAL2", or "OSC1" and "OSC2", or something similar)
that are designed to be directly connected to the 2 pins of a crystal.
(Capacitors from those pins to VCC and GND are also part of the recommended circuit).
An inverter inside the microcontroller acts as the amplifier, and the crystal and capacitors make up the rest of the oscillator.
In systems with multiple CPUs, it is often simpler, cheaper, and more reliable (avoiding metastability problems) to use a single crystal (rather than a dedicated crystal for each CPU).
CPUs (and many other components) often have a single "CLK" pin designed to be connected to the wire used to send that "clock signal" (a fixed frequency) everywhere.
Unfortunately, many people confuse the "clock signal" generated by an oscillator (a simple metronome beat, tone, at constant frequency) with far more complicated "clock system"s that keep track of seconds, minutes, hours, and sometimes days, weeks, months, and years.
for further reading
