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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.
For power-of-2 integer division, a simple binary counter can be used, clocked by the input signal. The least-significant output bit alternates at 1/2 the rate of the input clock, the next bit at 1/4 the rate, the third bit at 1/8 the rate, etc. An arrangement of flipflops is a classic method for integer-n division. Such division is frequency ...
Most frequency counters work by using a counter, which accumulates the number of events occurring within a specific period of time.After a preset period known as the gate time (1 second, for example), the value in the counter is transferred to a display, and the counter is reset to zero.
The green trace is the output from the dual-modulus prescaler, which happens to correspond to 7.1714 MHz in the case that the prescaler is at 128 and 7.1158 when it is at 129. It is plainly obvious that the modulus control is low for precisely 6 cycles of the prescaler output.
This prescaler can be reconfigured by software during run-time, allowing the clock speed to be optimized. Since all operations (excluding multiplication and 16-bit add/subtract) on registers R0–R31 are single-cycle, the AVR can achieve up to 1 MIPS per MHz, i.e. an 8 MHz processor can achieve up to 8 MIPS.
Many radio applications require frequencies that are higher than can be directly input to the digital counter. To overcome this, the entire counter could be constructed using high-speed logic such as ECL, or more commonly, using a fast initial division stage called a prescaler which reduces the frequency to a manageable level. Since the ...
Clock rate or clock speed in computing typically refers to the frequency at which the clock generator of a processor can generate pulses used to synchronize the operations of its components. [1] It is used as an indicator of the processor's speed. Clock rate is measured in the SI unit of frequency hertz (Hz).
Core speed of some microcomputers (relatively common in Motorola 68000 family); bus clock; double to 33.33 MHz, quadruple to 66.67 MHz, multiply by 6 to 100 MHz; IOAPIC clock speed, half the PCI bus frequency 16.777216 2 24 allows binary division to 1 Hz and 32.768 kHz. Real-time clock; also for DDS generators with 1 Hz step 16.800 1200