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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}}}
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 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.
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.
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.
The generator may have additional sections to modify the basic signal. The 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 ...
The frequency accuracy relative to the clock frequency is limited only by the precision of the arithmetic used to compute the phase. [4] NCOs are phase- and frequency-agile, and can be trivially modified to produce a phase-modulated or frequency-modulated output by summation at the appropriate node, or provide quadrature outputs as shown in the ...
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 ...