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A frequency divider, also called a clock divider or scaler or prescaler, is a circuit that takes an input signal of a frequency, , and generates an output signal of a frequency: f o u t = f i n N {\displaystyle f_{out}={\frac {f_{in}}{N}}}
A prescaler is an electronic counting circuit used to reduce a high frequency electrical signal to a lower frequency by integer division.The prescaler takes the basic timer clock frequency (which may be the CPU clock frequency or may be some higher or lower frequency) and divides it by some value before feeding it to the timer, according to how the prescaler register(s) are configured.
Using frequency dividers, frequency multipliers and phase locked loop circuits, it is practical to derive a wide range of frequencies from one reference frequency. The UART column shows the highest common baud rate (under 1,000,000), assuming a clock pre-divider of 16 is resolved to an exact integer baud rate. Though some UART variations have ...
A phase-locked loop or phase lock loop (PLL) is a control system that generates an output signal whose phase is fixed relative to the phase of an input signal. Keeping the input and output phase in lockstep also implies keeping the input and output frequencies the same, thus a phase-locked loop can also track an input frequency.
The frequency resolution, defined as the smallest possible incremental change in frequency, is given by [6] F r e s = F c l o c k 2 N {\displaystyle F_{res}={\frac {F_{clock}}{2^{N}}}} (2) Equation (1) shows that the phase accumulator can be thought of as a programmable non-integer frequency divider of divide ratio Δ F / 2 N {\displaystyle ...
It is measured in the SI unit of frequency hertz (Hz). The clock rate of the first generation of computers was measured in hertz or kilohertz (kHz), the first personal computers (PCs) to arrive throughout the 1970s and 1980s had clock rates measured in megahertz (MHz), and in the 21st century the speed of modern CPUs is commonly advertised in ...
A crystal oscillator is an electronic oscillator circuit that uses a piezoelectric crystal as a frequency-selective element. [1] [2] [3] The oscillator frequency is often used to keep track of time, as in quartz wristwatches, to provide a stable clock signal for digital integrated circuits, and to stabilize frequencies for radio transmitters and receivers.
Suppose that the programmable divider, using N, is only able to operate at a maximum clock frequency of 10 MHz, but the output f o is required to be in the hundreds of MHz range. Interposing a fixed prescaler that can operate at this frequency range with a division ratio M of, say, 40 drops the output frequency into the operating range of the ...