Implementing C language nested assembly language in KEIL

1. Background

In the process of learning MCU, it is very necessary to master some assembly language. As a low-level language, assembly language plays an irreplaceable role in MCU development. For example, each instruction can accurately determine the delay time, which is easy to understand and very suitable for hardware engineers to learn. However, to improve MCU skills, you must master C language programming, because C language has a powerful modular management concept. I think that in the process of learning, many people have learned both assembly language and C language, so a problem arises. If C language and assembly language are combined to achieve better programming effects, this explanation is based on this problem.

2. Operation steps

first step:

Create a new project and file in KEIL and copy the following program and save it as a C file:

/*

Function: Nesting assembly language in C language, which serves as a starting point for discussion

Author: Yang Rongguo of Sanwei Electronics

Date: 2010-5-16

*/

#include

delay()

{

int i,j;

for(i=0;i<1000;i++)

for(j=0;j<120;j++); //12M crystal oscillator delay 1MS

}

main()

{

P2=0x00; //Control 8 LEDs to light up

delay(); //delay 1S

#pragma ASM // assembly nesting starts

MOV P2,#0FFH //End of assembly nesting

#pragma ENDASM // assembly nesting starts

while(1); //C program ends

}

Step 2:

Select the C file in the Project window, such as CX1.C, and right-click, select "Options for ...", click "Generate Assembler SRC File" and "Assemble SRC File" on the right, and change the checkbox from gray to black (double-click);

Step 3:

Add the corresponding library file (e.g. Keil\C51\Lib\C51S.Lib in Small mode) to the project. This file must be the last file of the project (load it into the project like a header file);

Step 4:

Compile and generate HEX file in KEIL, and design the simulation diagram as shown below, and check the effect in simulation.

3. Demonstration Effect

As shown in the figure below, if you can see the 8 LEDs controlled by the P2 port of the microcontroller light up first and then automatically turn off after a delay of about 1S on your own simulation software PROTEUS, it means that you have fully mastered the method of nesting assembly language in C language.

Homework: Implement C language nested in assembly language. Use C language to control the red LED of P2.0 to flash 5 times at a time interval of 0.1S. Use assembly language to control the green LED of P2.1 to flash 3 times at a time interval of 0.1S and then stop.