electric pulse
A periodic process of pulse current can be regarded as an electric pulse and a signal.
Compared with the continuous signal that appears for a short time in the whole signal period, there is no signal in most signal periods. Just like a person's pulse. Now it generally refers to digital signals, and there is a signal half the time (or even longer) in a cycle. The signal in the computer is a pulse signal, also known as a digital signal.
Pulse circuit is a circuit specially used to generate electric pulses and amplify, transform and shape them.
The pulse shaping program can produce different pulse waveforms, and the optimal pulse waveform is different according to different applications.
In digital circuits (computers), the 1 state and the 0 state are represented by high level and low level respectively. At this time, the waveform of the electrical signal is non-sinusoidal, and it is a pulse signal, also known as a digital signal.
Statement 1: In a sequential logic circuit, a stable and accurate clock pulse signal is usually needed to control the synchronous and coordinated work of flip-flops.
Statement 2: In synchronous sequential circuits, rectangular pulses are used as clock signals to control and coordinate the work of the whole system.
When the internal period is less than the worst-case internal propagation delay, most sufficiently complex integrated circuits use clock signals to synchronize different parts of the circuit.
Quote an explanation from Zhihu:
CPU can be roughly regarded as many, many small capacitors (1 when fully charged, and 0 when not fully charged), and these small capacitors are charged and discharged over and over again in every calculation.
Many small capacitors make up basic modules, such as input to output. There is a delay from input to output, because as I said before, it takes time to charge and discharge the capacitor.
Basic small modules are connected in various ways to form complex functions, that is, the output of the former small module will be used as input by the latter module.
The module connection line is functional, so how can the later module know whether the previous module has completed charging and discharging or is charging and discharging? On the other hand, the longer the path, the longer the time from the initial input to the final output, that is, different path lengths have different delays, so it is difficult to ensure that the data on each pin arrives strictly at the same time.
Therefore, the clock mechanism is introduced: a unified clock pulse is used to synchronize the small modules. The pulse didn't come, so the small module took the time to charge and discharge. When the pulse comes, the modules move together. You can simply think that when the clock pulse comes, the CPU moves. If the next clock pulse does not come, the CPU will not move.
(In order to ensure the operation, data reading and writing calculation must be carried out in strict order. )
The clock edge trigger signal means that all state changes occur at the moment when the clock edge arrives. Only when the synchronization signal comes, the related flip-flops will change the output state according to the input signal, so that the related electronic components can work synchronously. Whether the state quantity of the control logic unit changes with the rising edge or falling edge of the clock signal depends on the specific logic design.
The clock does not act on the ALU (Logic Control Unit), but on the register. This special register is called the clock register. Writing can only be done on the rising edge of the clock signal (such as the high bit of 5V). At other times, the input can only wait outside.
Clock frequency (also translated as clock speed, English) refers to the basic frequency of the clock in the synchronous circuit, with "several cycles per second" as the unit of measurement, and the unit of measurement is SI unit -Hz. It is an important index to evaluate CPU performance.
For example, the reference frequency from a crystal oscillator is usually equal to a fixed sine wave, so the clock frequency is this reference frequency, and the electronic circuit will convert it into a corresponding pulse square wave for digital electronic equipment.
The clock signal is a rectangular pulse, and there are two ways to obtain the rectangular pulse:
Of course, when the rectangular pulse is obtained by shaping method, the premise is to find an existing voltage signal whose frequency and amplitude meet the requirements.