About MCU C interrupt function-EEWORLD

Collect

Define interrupt service function

Function type function name (formal parameters) interrupt n [using n]

Interrupt Number Interrupt Source Interrupt Vector

0 External interrupt 0 0003H

1 Timer/Counter 0 000BH

2 External interrupt 1 0013H

3 Timer/Counter 1 001BH

4 Serial port 0023H

The interrupt keyword is indispensable. It tells the compiler that this function is an interrupt service function.

n indicates the interrupt number used. The value range of n is 0-31, but the specific interrupt number depends on the chip model, such as

AT89C51 actually uses interrupts 0 to 4. Each interrupt number corresponds to an interrupt vector, the specific address is 8n+3,

After the interrupt source responds, the processor will jump to the address where the interrupt vector is located to execute the program. The compiler will generate a

Unconditional jump statement jumps to the address where the interrupt service function is located to execute the program. The following table shows the interrupt vector and the interrupt vector of the 51 chip.

Disconnected number.

Qmt above has roughly introduced the definition of interrupt function to you. It is worth mentioning that the interrupt function type is void, which means that the interrupt function cannot have a return value. This point should be made clear, so do not try to let the interrupt function give you a return value. In addition, there are no parameters in the brackets after the function name... This also needs to be noted that the interrupt function cannot pass parameters.

The dot after interrupt is the interrupt number. Let me explain using to you.

This is a keyword extended by the C51 compiler. It is used to select different register groups in the 80c51 microcontroller. As you know, there are 4 groups of R0-R7, so the number after using is a number in the range of 0-3. If using is not required, the compiler will automatically select a group of registers as absolute register access.

Using has a certain impact on the code.

Let me give you a simple example. You can think about it.

If you define

void time0() interrupt 1 using 1

Suppose we call a delay() in the interrupt; this delay has a delay effect.

Then, we need to make sure that we are using the same set of registers, otherwise, confusion will occur.

Do you understand what I mean?

So, I suggest you not to use using when it is not necessary. However, you can try this keyword.

I wish you good luck in your studies.

LX efenwu:

In short, 51 has 4 groups of general registers, R0~R7. When we use them, we never specify which R0 is used, and the compiler will automatically select a group of general registers as absolute address access. In C language, when we write a function, such as a delay function, the variables used in it are using R0-R7 after disassembly, so can you be sure which group of registers you are using?

So, using using can select the register bank to use, but at the same time, you must be especially careful when "switching". If you call other programs in the interrupt program, the register bank switching problem will occur.

Actually, there are other things to note about using. Because it is troublesome to use, I never use this keyword. This is why I don't recommend you to use using. The compiler will choose a group by itself.

So just define an interrupt function like this:

void FuncName() interrupt lvl

Where lvl is the priority number of the interrupt.

Keywords：MCU Reference address：About MCU C interrupt function

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