EE 308 -- LAB 04
C Programming Language
Introduction

The C programming language is used extensively in programming microprocessors. In this lab you will write some simple C programs which do the things you did in assembly language in the last lab.

For example, the following C program increments Port B:

    /* A C Language Program to Increment Port B on a 68HC11
     * Bill Rison
     * January 12, 1996
     */
    #include <hc11.h>            /* Get the HC11 definitions */
    #define D_100MS 6667         /* To delay 100 ms */
    #define TRUE  1              /* A normal C define */
    
    /* Function to delay 100 milliseconds */
    void delay_100ms(void)
    {
        int i;
  
        i = 0;
        while (i < D_100MS)
        {
            i = i + 1;
        }
    }
    
    void main()                  /* The main program */
    {
        while (TRUE)             /* Do forever */
        {
            PORTB = PORTB + 1;   /* Increment Port B */
            delay_100ms();       /* Wait 100 ms */
        }
    }

Pre-Lab

1. To use the C compiler in the lab, you need to initialize some environment variables for DOS. This is done by giving the following command at a DOS prompt:

   e:\icc11\iccsetup

2. Type in the above C program and give it the name inc.c. Compile the program with the following command:

   icc11 -l inc.c

   You should now have a file named inc.s in your directory. This is the assembly language file which the C compiler generated. Look at the file and try to understand what it does. Note that there will be some things which will not make sense to you. At the very least, find the assembly language code which adds one to what was in Port B, and stores it back into Port B. (Note that the C compiler produces assembly code in decimal rather than hexadecimal. Port B has an address of 0x1004, or 0d4100. You'll want to see where inc.s accesses address 4100.)

3. Using the above program as a model, write C programs to implement the other functions from Lab 3.