Clock cycle, oscillating cycle, machine cycle, CPU cycle, status cycle, command cycle, bus cycle, task cycle

Computer systems have a series of "Cycle" concepts. It is important to understand these concepts in a different and connected manner. The followingClock cycle, oscillating cycle, machine cycle, CPU cycle, status cycle, command cycle, bus cycle, task cycleFor a brief introduction.

Cycle

In electronic technology, the pulse signal is a pulse signal continuously sent at a certain voltage range and at a certain interval. The interval between pulses is called a cycle, and the number of pulses generated per unit time (for example, 1 second) is called a frequency. Frequency is the metering name that describes the number of pulses that appear in a periodic cycle signal (including a pulse signal) per unit time. The standard unit of measurement for a frequency is Hz ). The system clock in the computer is a typical Pulse Signal Generator with a very accurate and stable frequency.

Clock cycle

Clock cycle, also known as the oscillating cycle (if the output of the crystal oscillator is directly used as the CPU clock without frequency division, the clock cycle is equal to the oscillating cycle ), that is, the reciprocal of the operating frequency of the CPU crystal oscillator is the most basic and minimum time unit in the computer. It is usually a cycle pulse or a T cycle. For the single-chip microcomputer clock cycle, the clock cycle is the basic time unit of the single-chip microcomputer, two oscillation cycles (always cycle) constitute a state cycle.

 

Oscillation cycle(Oscillating period)

In the attenuation oscillation, the time between two adjacent peaks in the same direction is called the oscillation cycle TP, and the oscillation frequency is 2 π/TP. In the same attenuation ratio, the shorter the oscillation cycle or the higher the oscillation frequency, the shorter the recovery time. Therefore, the oscillation cycle (frequency) reflects the system response speed.

 

Machine cycle

The machine cycle, also known as the CPU cycle. In a computer, for ease of management, the execution process of a command is often divided into several stages (for example, commands, memory reads, and memory writes ), each stage completes a task (called a basic operation ). The time required to complete a basic operation is called the machine cycle. Generally, a machine cycle consists of several s cycles (State cycles.

 

CPU cycle

Also known as the machine cycle, the CPU cycle is defined as the shortest time for reading a script from the memory. A command cycle is usually composed of several CPU cycles.

Status cycle

 

In the 8051 microcontroller, a clock cycle is defined as a cycle (expressed by P), and two beats are defined as a state cycle (represented by S ).

 

 

One machine cycle of the 8051 series single-chip microcomputer is composed of six s cycles (State cycles. One machine cycle contains six state cycles (S1-S6), and one State cycle contains two clock oscillation cycles (clock cycles ). For example, the machine cycle of 8051 single-chip microcomputer is composed of six state cycles, that is, one machine cycle = six state periods = 12 clock periods.

Instruction cycle

 

The command cycle is the time required to execute a command, that is, the sum of time the CPU extracts a command from the memory and executes the command. Generally, it consists of several machine cycles, from Command taking, analysis command to all the time required for execution. The number of machine cycles varies depending on different commands. For some simple single-byte commands, after the commands are obtained into the instruction register during the instruction fetch cycle, the commands are decoded and executed immediately, and other machine cycles are no longer required. For some complex commands, such as transfer and multiplication commands, two or more machine cycles are required. Commands that contain one machine cycle are generally called single-cycle commands. commands that contain two machines are called dual-cycle commands.

 

Bus Cycle

 

A bus cycle usually refers to the time required to complete a memory read/write operation or an input/output device read/write operation through the bus. Because the memory and I/O ports are attached to the bus, the CPU accesses the memory and I/O interfaces through the bus. Generally, the time required for a CPU to access the microprocessor (memory or I/O interface) through the bus is called a bus cycle. A bus cycle generally contains four clock cycles. These four clock cycles are called four states: T1, T2, T3, and T4.

Task cycle

A cyclic task is a task instance in which the computer system reaches and requests to run in a certain period. Each request is called a task instance. The start time of a task instance is the arrival time of the task instance, the time when the task instance is set to the ready state is the time when the task instance is released.