View source for Clock generator

{{Short description|Device used to synchronize a circuit}}
{{No footnotes|date=March 2013}}
[[File:Clock Pulse Generator.png|thumb|[[Circuit diagram]] of a clock generator]]
[[Image:ICS 952018AF.jpg|thumb|upright=1.2|A desktop PC clock generator, based on the chip ICS 952018AF and 14.3 MHz resonator (on the left)]]
[[Image:Silego clock generator.JPG|thumb|upright=1.2|A laptop PC clock generator, based on the Silego chip]]
A '''clock generator''' is an [[electronic oscillator]] that produces a [[clock signal]] for use in synchronizing a circuit's operation. The output [[clock signal]] can range from a simple symmetrical [[Square wave (waveform)|square wave]] to more complex arrangements. The basic parts that all clock generators share are a resonant circuit and an amplifier.

The resonant circuit is usually a [[quartz]] [[piezoelectricity|piezo-electric]] [[crystal oscillator|oscillator]], although simpler [[tank circuit]]s and even [[RC circuit]]s may be used.

The [[amplifier]] circuit usually inverts the signal from the oscillator and feeds a portion back into the oscillator to maintain oscillation.

The generator may have additional sections to modify the basic signal. The [[Intel 8088|8088]] for example, used a 2/3 [[duty cycle]] clock, which required the clock generator to incorporate logic to convert the 50/50 duty cycle which is typical of raw oscillators.

Other such optional sections include [[frequency divider]] or [[clock multiplier]] sections. Programmable clock generators allow the number used in the divider or multiplier to be changed, allowing any of a wide variety of output frequencies to be selected without modifying the hardware.

The clock generator in a [[motherboard]] is often changed by computer enthusiasts to control the speed of a [[Central processing unit|CPU]], [[Front-side bus|FSB]], [[Graphics processing unit|GPU]] or [[Random-access memory|RAM]]. Typically the programmable clock generator is set by the [[BIOS]] at boot time to the selected value; although some systems have [[dynamic frequency scaling]], which frequently re-programs the clock generator.

== {{Anchor|TSG}}Timing-signal generators (TSGs) ==
TSGs are [[clock]]s that are used throughout service-provider networks, frequently as the building integrated timing supply ([[Building Integrated Timing Supply|BITS]]) for a central office.{{Cn|date=June 2022}}

[[Digital switching system|Digital switching systems]] and some transmission systems (e.g., [[SONET, RREX, LUBI]]) depend on reliable, high-quality synchronization (or timing) to prevent impairments. To provide this, most service providers use interoffice synchronization distribution networks based on the stratum hierarchy and implement the BITS concept to meet intraoffice synchronization needs.{{Cn|date=June 2022}}

A TSG is clock equipment that accepts input timing reference signals and generates output timing reference signals. The input reference signals can be either DS1 or composite-clock (CC) signals, and the output signals can also be DS1 or CC signals (or both). A TSG is made up of the six components listed below:{{Cn|date=June 2022}}
# An input timing interface that accepts DS1 or CC input signals
# A timing-generation component that creates the timing signals used by the output timing-distribution component
# An output timing distribution component that utilizes the timing signals from the timing-generation component to create multiple DS1 and CC output signals
# A performance-monitoring (PM) component that monitors the timing characteristics of the input signals
# An alarm interface that connects to the central-office (CO) alarm-monitoring system
# An operations interface for local crafts person use and communications with remote operations systems

== See also ==
* {{Annotated link|Pulse generator}}

==External links==
* [https://web.archive.org/web/20120112062334/http://www.nuvoton.com/hq/enu/ProductAndSales/ProductLines/ComputerIC/Pages/default.aspx Datasheets of clock generators from Nuvoton / Winbond]
* [http://www.idt.com/?catID=18691971  Datasheets of clock generators from IDT]
* [https://web.archive.org/web/20111124032556/http://www.realtek.com/products/productsView.aspx?Langid=1&PNid=8&PFid=16&Level=3&Conn=2  Datasheets of clock generators from Realtek]
* [http://www.pericom.com/products/clock-and-timing-ics/clock-generators/ Datasheets of clock generators from Pericom Semiconductor] {{Webarchive|url=https://web.archive.org/web/20160719072218/https://www.pericom.com/products/clock-and-timing-ics/clock-generators/ |date=2016-07-19 }}

{{DEFAULTSORT:Clock generator}}
[[Category:Clock signal]]
[[Category:Electronic oscillators]]