Interrupt knowledge point set

​ Catalog ​

​ ​ One 、 What is interruption ​​

​ ​ Two 、 Interrupt the whole process ​​

​ ​ 3、 ... and 、 Interrupt type ​​

​ ​ Four 、 Interrupt source ​​

​ ​ 5、 ... and 、 Interrupt priority ​​

​ ​ 6、 ... and 、 Interrupt mask ​​

​ ​ 7、 ... and 、 Break nesting ​​

​ ​ 8、 ... and 、 Vector break ​​

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One 、 What is interruption

according to 《 Teacher's Encyclopedia Dictionary 》 Description in ： Interruption refers to the process of computer operation , When there are some unexpected situations requiring host intervention , The machine can automatically stop the running program and transfer to the program dealing with the new situation , After processing, return to the original suspended program to continue running .

The interrupt system of single chip microcomputer is an important part of computer . real-time control 、 Automatic troubleshooting 、 Interrupt system is often used for data transmission between computer and peripheral equipment . The application of interrupt system greatly improves the computer efficiency .

Two 、 Interrupt the whole process

The whole process of interrupt refers to the process starting from the interrupt request sent by the interrupt source ,CPU In response to this request , The current program was interrupted , Go to interrupt service program , Until the interrupt service program is executed ,CPU Return to the original program and continue the whole process .

Most interrupt systems have the following operations , These operations are arranged according to the execution order of interrupts ：

① Receive interrupt request .

② Check the interrupt mask bit of this level , If the bit is 1 Then the interrupt source of the current level participates in the priority queue .

③ Interrupt priority selection .

④ After the processor executes an instruction, or the instruction cannot be executed , Then immediately suspend the current procedure . next , The interrupt unit specifies the corresponding main memory unit according to the interrupt level , The interrupted instruction address and the current main state information of the processor are stored in this unit .

⑤ The interrupt unit specifies another main memory unit according to the interrupt level , Take out the new status information of the processor and the starting address of the interrupt control program of this level from these units .

⑥ Execute interrupt control program and corresponding interrupt service program .

⑦ After executing the interrupt service program , Use special instructions to make the processor return to the interrupted program or turn to other programs .

The data of registers and memory used by interrupt service program will be overwritten , Interrupts are returned , So it is usually necessary to protect the site . The method is to push the content to be protected onto the stack .

3、 ... and 、 Interrupt type

Hard interrupt , The signal comes from the outside of the chipset .

• • 
    
• Maskable interrupt
• Non maskable interrupt
• Processor interrupt
• Pseudo interrupt
  • 
    

Soft interrupt ： This is generally called system call , As the name suggests, it is an interrupt set by software . It is a software operation that needs to cause CPU Attention .

Four 、 Interrupt source

An interrupt source is the cause of an interrupt .

①　 The machine broke down .

②　 Procedural interruption . Some machines call programmatic interrupts “ abnormal ”, Not called interrupt .

③　 Input － Output device interrupt .

④　 External interruption .

⑤　 Call the manager .

5、 ... and 、 Interrupt priority

Several interrupt requests may occur at the same time , But the interrupt system can only respond and process in a certain order . The interrupt that can be responded to first has the highest priority , Process in order of priority . The priority level is determined by the interrupt queue line of the interrupt component .

6、 ... and 、 Interrupt mask

Corresponding mask bits are set corresponding to each interrupt level . Only the mask bit is 1 when , Only this interrupt level can participate in the interrupt priority queue . The interrupt mask bit can be established by a special instruction , Therefore, the interrupt priority can be flexibly adjusted . Some machines also set the mask bit for some interrupt sources , Only the mask bit is 1 when , The corresponding interrupt source works .

7、 ... and 、 Break nesting

When CPU When responding to an interrupt , If an interrupt source with high priority sends an interrupt request , be CPU Can interrupt the ongoing interrupt service program , And keep the breakpoint of the program （ Similar to subroutine nesting ）, Respond to advanced interrupts , After advanced interrupt processing , Then continue the interrupted interrupt service program , This process is called interrupt nesting . If the priority level of the interrupt source issuing the new interrupt request is the same as or lower than the interrupt source being processed ,CPU Will not respond to this interrupt request , New interrupt requests cannot be processed until the interrupt service program being processed is executed .

8、 ... and 、 Vector break

Set a vector for each interrupt source . These vectors are sequentially stored in a specific memory area of the main memory . The contents of the vector are the starting address of the corresponding interrupt service program and the processor status word . In response to an interrupt , The interrupt system hardware provides the vector address , The processor obtains the vector according to the address , And transfer to the corresponding interrupt service program    .