Basic workflow of CPU

CPU The internal structure of

1、 arithmetic logic unit ALU

ALU It's the core of the arithmetic unit , It is based on the full adder , It is a circuit composed of registers and corresponding control logic , Under the action of the control signal, the addition can be completed 、 reduce 、 ride 、 Divide by four operations and various logical operations , As mentioned just now . This is equivalent to the production line in the factory , Responsible for computing data .

2、 Register group Rs

Rs Is essentially CPU Where data is temporarily stored in , It holds the data waiting to be processed , Or data that has been processed ,CPU It takes less time to access registers than to access memory , Using registers can reduce CPU Number of memory accesses , So as to improve CPU Working speed of , However, due to the limitation of chip area and integration , The capacity of a register group cannot be large , Register group can be divided into special register and through register , The function of special register is fixed , Register the corresponding data separately , The register has a wide range of ways, and its purpose can be specified by the programmer , The number of general purpose registers varies from microprocessor to microprocessor .

3、 control unit

Just like the Logistics Distribution Department of the factory , The control unit is the whole CPU Command and control center , By the instruction register 、 Instruction decoder 、 And operation controller , It is very important to coordinate the orderly work of the whole computer , It's based on the user's pre programmed program , In this way, each instruction is taken from the memory , Put it in the instruction memory and determine what operation should be carried out through the analysis of the instruction decoder , Finally, the controller is operated in time sequence , Send micromanipulation control signals to corresponding components , Operating the controller , It mainly includes Beat generator Control matrix Clock generator , Reset circuit, start stop circuit and other control logic .

4、 Bus

Just like the communication channels between various parts of the factory , A bus is actually a set of wires , It is a collection of various common signal lines , A public highway used to transmit information as all components of a computer , Direct sum CPU Connected bus , These include data bus Address bus Control bus The library bus is used to transmit data information Used to transfer addresses to the bus CPU Address information sent , The control bus is used to transmit control signals , Timing signal and status information, etc .

CPU Workflow process

Program = Instructions + data

working principle ：

in general ,cpu Instructions and corresponding data are taken out one by one from memory , According to the instruction opcode , Perform arithmetic processing on data and , Until the program is finished , The specific process can be divided into the following four steps .

1 Take command

cpu The controller reads an instruction from memory and places it in a register

2 Instruction compilation

The instructions in the instruction register are decoded , Feel that you should do that , Where are the operands

3 Execution instruction

The execution of instructions is divided into two steps ： Take operands and perform operations .

Fetching operands ：CPU Read operands from memory to register through addressing operation , Save it for the time being

Carry out operations ： The arithmetic unit passes the opcode in the instruction , Operate on the number in the register

4 Command count

Modify the instruction counter , Determine the address of the next instruction .cpu Repeat the three steps above , The instructions in the memory code segment are executed one by one , Until the end of the program .