CPU The function and basic structure of

CPU The function of

1. The central processing unit is composed of arithmetic unit and controller .
   1. Arithmetic unit ： Process the data
   2. controller ： Be responsible for coordinating and controlling the instruction sequence of computer components to execute programs ( Take command 、 Analysis instructions 、 Execution instruction )
   3. function ： Command control 、 Operational control 、 time control 、 The data processing 、 Interrupt handling

CPU Basic structure

1. Arithmetic unit

2. controller

Instruction execution process

Instruction cycle

A complete instruction cycle should include values 、 Inter site 、 Execution and interruption 4 A cycle .

• The addressing period is Take command
• The inter address period is Take a valid address
• The execution cycle is Fetching operands
• The interruption period is Save program breakpoints

Instruction cycle data flow

Take the period ： according to PC Take the instruction code from the main memory and store it in IR in

• PC → MAR → Address bus → Main memory
• CU → Control bus → Main memory
• Main memory → data bus → MDR → IR
• CU → PC

Interval period ： Fetch the valid address of the operand

• IR → MAR → Address bus → Main memory
• CU → Control bus → Main memory
• Main memory → data bus → MDR

Execution cycle ： Fetching operands , And according to IR The opcode of the instruction word in passes ALU Operations produce execution results

Interrupt cycle ： Save breakpoints , Send interrupt vector , Processing interrupt requests

Instruction execution scheme

Single instruction cycle

1. Choose the same execution time for all instructions
2. Between instructions Serial execution
3. The instruction cycle depends on the execution time of the instruction with the longest execution time
4. It will reduce the running speed of the whole system

Multiple instruction cycles

1. Choose different execution steps for different types of instructions
2. Between instructions Serial execution
3. Need more complex hardware design

Pipeline solution

1. Instructions can Parallel execution The plan

Function and basic structure of data path

The function of data path

The path through which data is transferred between features is called Data access

The function of data path is Realization CPU Internal arithmetic unit and register and data exchange between registers

The basic structure of data path

• An internal bus is the same component
• System bus refers to the components of the same computer system

1. Data transfer between registers

//  With PC For example 
PC → Bus	Pcount It works ,PC Content delivery bus 
Bus → MAR	MARin It works , The bus content is sent to MAR

2. Main memory and CPU Data transfer between

//  With CPU Take reading instructions from main memory as an example 
PC → Bus → MAR		PCout and MARin It works 
1 → R 				CU Issue a read command 
MEM(MAR) → MDR		MDRin It works 
MDR → Bus → IR 		MDRout and IRin It works 

3. To perform arithmetic or logical operations

//  Take addition as an example 
Ad(IR) → Bus → MAR		MDRout and MARin It works 
1 → R					CU Issue a read command 
MEM →  cable  → MDR		
	
MDR → Bus → Y
(ACC) → (Y) → Z
Z → ACC

notes ： Understand together with the above figure

Function and working principle of the controller

Structure and function of the controller