Writing of MCU interrupt function

interrupt m modifier

The C51 interrupt function must be modified by this modifier. In C51 programming, when the interrupt m modifier is used in the function definition, the system converts the corresponding function into an interrupt function during compilation, automatically adds the program header and trailer, and automatically arranges it in the corresponding position in the program memory according to the 51 system interrupt processing method.

In this modifier, the value of m is 0~31, and the corresponding interrupt conditions are as follows:

0——External interrupt 0

1——Timer/Counter T0

2——External interruption 1

3——Timer/Counter T1

4——Serial port interrupt

5——Timer/Counter T2

Other values ​​are reserved.

The C51 compiler generates an interrupt vector from the absolute address 8m+3, where m is the interrupt number, which is the number after interrupt. The vector contains an absolute jump to the entry address of the interrupt function.

[Example] Write an interrupt service program to count the number of interrupts of external interrupt 0

1 int  x=0;2 void  int0()  interrupt 0  using 13 {4   x++;5 }

using n modifier

The modifier using n is used to specify the working register group used within this function, where n is a value between 0 and 3, indicating the register group number. This modifier can be omitted, and the system automatically selects the register group number after it is omitted.

Note the following about the interrupt function:

(1) Interrupt functions cannot pass parameters. If an interrupt function contains any parameter declaration, a compilation error will occur.

(2) The interrupt function has no return value. If you attempt to define a return value, you will not get the correct result. It is recommended to define the interrupt function as a void type to clearly indicate that there is no return value.