Basic example of writing C code for the 8051

/*************************************************************************

* basic.c - The basics of writing C code for the 8051 using the Keil

* development environment. In this case, a simple program will be

* constructed to make a binary counter on Port 0.

*/

/*

* As always with C, the included header files should come first. Most

* every project for the 8051 will want to include the file reg51.h. This

* header file contains the mapping of registers to names, such as setting

* P0 (port 0) to address 0x80. This allows the coder to use the keyword

* "P0" in their code whenever they wish to access Port 0. For the complete

* list of registers named, view the file.

*/

#include

/*

* Other header files may be included after reg51.h, including any headers

* created by the user.

*/

/*

* The C program starts with function main(). In the case of a program

* written using multiple .c files, main can only occur in one of them.

* Unlike in programming user applications for a standard computer, the

* main() function in a Keil program for the 8051 takes no inputs and

* returns no output, thus the declaration has implied void types.

*/

/*************************************************************************

* main - Program entry point

*

* INPUT: N/A

* RETURNS: N/A

*/

main()

{

unsigned int i; /* will be used for a delay loop */

/* First, Port 0 will be initialized to zero */

P0 = 0;

/*

* Now the counter loop begins. Because this program is intended

* to run in an embedded system with no user interaction, and will

* run forever, the rest of the program is placed in a non-exiting

* while() loop.

*/

while (1==1)

{

/*

* This is a very unpredictable method of implementing a delay

* loop, but remains the simplest. More reliable techniques

* can be done using the using the built-in timers. In this

* example, though, the for() loop below will run through 60000

* iterations before continuing on to the next instruction.

* The amount of time required for this loop varies with the

* clock frequency and compiler used.

*/

for (i = 0; i <>

/* Increment Port 0 */

P0 = P0 + 1;

}

}