1. H. Huang Transparency No.4-1 The 68HC11 Microcontroller Chapter 4: C Language Programming The 68HC11 Microcontroller Han-Way Huang Minnesota State University, Mankato

2. H. Huang Transparency No.4-2 The 68HC11 Microcontroller Introduction to C - C has gradually replaced assembly language in many embedded applications. - A summary of C language constructs that will be used in 68HC11 programming. - Books on C language 1.Kernighan & Ritchie, “The C Programming Language”, Prentice Hall, 1988. 2.Deitel & Deitel, “C: How to Program”, Prentice Hall, 1998. 3.Kelly & Pohl, “A Book on C: Programming in C”, Addison-Wesley, 1998. - A C program consists of functions and variables. - A function contains statements that specify the operations to be performed. - Types of statements: 1.Declaration 2.Assignment 3.Function call 4.Control 5.Null - A variable stores a value to be used during the computation. - The main () function is required in every C program.

3. H. Huang Transparency No.4-3 The 68HC11 Microcontroller A C Program Example (1)#include -- causes the file stdio.h to be included (2)/* this is where program execution begins */ -- a comment (3)main () -- program execution begins (4){ -- marks the start of the program (5) inta, b, c; -- declares three integer variables a, b, and c (6) a = 3; -- assigns 3 to variable a (7) b = 5; -- assigns 5 to variable b (8) c = a + b; -- assigns the sum of a and b to variable c (9) printf (“ a + b = %d\n”, c); -- prints the string a + b = followed by value of c (10) return 0; -- returns 0 to the caller of main( ) (11) } -- ends the main( ) function Types, Operators, and Expressions - variables must be declared before they can be used. - A variable declaration must include the name and type of the variable and may optionally provide its initial value.

4. H. Huang Transparency No.4-4 The 68HC11 Microcontroller -The name of a variable consists of letters and digits. - The underscore character “_” can be used to improve readability of long variables. Data Types -C has four basic data types: char, int, float, and double. -A variable of type char can hold a single byte of data. -A variable of type int is an integer that is the natural size for a particular machine. -The type float refers to a 32-bit single-precision floating-point number. -The type double refers to a 64-bit double-precision floating-point number. -Qualifiers short and long can be applied to integers. For ImageCraft C compiler, short is 16 bits and long is 32 bits. -Qualifiers signed and unsigned may be applied to data types char and integer. Declarations -A declaration specifies a type, and contains a list of one or more variables of that type.

5. H. Huang Transparency No.4-5 The 68HC11 Microcontroller Examples of declarations int i, j, k; char cx, cy; int m = 0; char echo = ‘y’;/* the ASCII code of letter y is assigned to variable echo. Constants -There are four kinds of constants: integers, characters, floating-point numbers, and strings. -A character constant is written as one character within single quotes, such as ‘x’. A character constant is represented by the ASCII code of the character. -A string constant is a sequence of zero or more characters surrounded by double quotes, as “68HC11 is made by Motorola” or “”, which represented an empty string. Each individual character in the string is represented by its ASCII code. -An integer constant like 1234 is an int. A long constant is written with a terminal l or L, as in 44332211L.

6. H. Huang Transparency No.4-6 The 68HC11 Microcontroller -A number in C can be specified in different bases. The method to specify the base of a number is to add a prefix to the number: Arithmetic Operators +add and unary plus -subtract and unary minus * multiply /divide -- truncate quotient to integer when both operands are integers. %modulus (or remainder) -- cannot be applied to float or double ++increment (by 1) --decrement (by 1)

7. H. Huang Transparency No.4-7 The 68HC11 Microcontroller Bitwise Operators -C provides six operators for bit manipulations; they may only be applied to integral operands. &AND |OR ^XOR ~NOT >>right shift << left shift -& is often used to clear one or more bits of an integral variable to 0. PORTD = PORTD & 0xBD/* clears bit 6 and bit 1 of PORTD to 0 */ /* PORTD is of type char */ -| is often used to set one or more bits to 1. PORTB = PORTB | 0x40;/* sets bit 6 to 1 (PORTB is of type char) */ -^ can be used to toggle a bit. abc = abc ^ 0xF0;/* toggles upper four bits (abc is of type char) */

8. H. Huang Transparency No.4-8 The 68HC11 Microcontroller ->> can be used to shift the involved operand to the right for the specified number of places. xyz = xyz >> 3;-- shift right 3 places -<< can be used to shift the involved operand to the left for the specified number of places. xyz = xyz << 4;-- shift left 4 places -The assignment operator = is often combined with the operator. For example, PORTD &= 0xBD; PORTB |= 0x40; xyz >>= 3; xyz <<= 4;

9. H. Huang Transparency No.4-9 The 68HC11 Microcontroller Relational and Logical Operators -Relational operators are used in expressions to compare the values of two operands. -The value of the expression is 1 when the result of comparison is true. Otherwise, the value of the expression is 0. -Relational and logical operators: ==equal to !=not equal to >greater than >=greater than or equal to <less than <=less than or equal to &&and ||or !not (one’s complement)

10. H. Huang Transparency No.4-10 The 68HC11 Microcontroller Examples of Relational and Logical Operators: if (!(ADCTL & 0x80) statement 1 ;/* if bit 7 is 0, then execute statement 1 */ if (i 0) statement 2 ;/* if 0 < i < 10 then execute statement 2 */ if (a1 == a2) statement 3 ;/* if a1 = a2 then execute statement 3 */ Control Flow -The control-flow statements specify the order in which computations are performed. -Semicolon is a statement terminator. -Braces { and } are used to group declarations and statements together into a compound statement, or block.

11. H. Huang Transparency No.4-11 The 68HC11 Microcontroller If-Else Statement if (expression) statement 1 else-- The else part is optional. statement 2 Example, if (a != 0) r = b; else r = c; A more concise way for this statement is r = (a != 0)? b : c;

12. H. Huang Transparency No.4-12 The 68HC11 Microcontroller Multiway Conditional Statement if (expression1) statement 1 else if (expression2) statement 2 else if (expression3) statement 3 … else statement n Example, if (abc > 0) return 5; else if (abc = 0) return 0; else return -5;

13. H. Huang Transparency No.4-13 The 68HC11 Microcontroller Switch StatementExample switch (expression) {switch (i) { case const_expr 1 ;case 1: printf(“#”); statement 1 ;break; break;case 2: printf(“##”); case const_expr 2 ;break; statement 2 ;case 3: printf(“###”);break; …case 4: printf(“####”); default:break; statement n ;case 5: printf(“#####”); }break; }

14. H. Huang Transparency No.4-14 The 68HC11 Microcontroller For-Loop Statement for (expr1; expr2; expr3) statement; where, expr1 and expr2 are assignments or function calls and expr3 is a relational expression. Example sum = 0; for (i = 1; i < 10; i++) sum += i * i; for (i = 1; i < 20; i++) if (i % 2) printf(“%d “, i);

15. H. Huang Transparency No.4-15 The 68HC11 Microcontroller While Statement while (expression) statement Example int_cnt = 5; while (int_cnt);/* do nothing while the variable int_cnt  0 */ Do-While StatementExample doint digit = 9; statementdo while (expression);printf(“%d “, digit--); while (digit >= 1);

16. H. Huang Transparency No.4-16 The 68HC11 Microcontroller Input and OutputExamples -Not part of the C language itself. -Four I/O functions will be discussed. 1.int getchar ( ). char xch; -- returns a character when calledxch = getchar (); 2.int putchar (int).putchar(‘a’); -- outputs a character on a standard output device 3.int puts (const char *s).puts (“Welcome to USA! \n”); -- outputs the string pointed by s on a standard output device 4.int printf (formatting string, arg1, arg2, …). -- converts, formats, and prints its arguments on the standard output device.

17. H. Huang Transparency No.4-17 The 68HC11 Microcontroller Formatting String for Printf -The arguments of printf can be written as constants, single variable or array names, or more complex expressions. -The formatting string is composed of individual groups of characters, with one character group associated with each output data item. -The character group starts with %. -The simplest form of a character group consists of the percent sign followed by a conversion character indicating the type of the corresponding data item. -Multiple character groups can be contiguous, or they can be separated by other characters, including whitespace characters. These “other characters” are simply sent to the output device for display. -Examples printf (“this is a challenging course ! \n”); printf(%d %d %d”, x1, x2, x3);/* outputs x1, x2, and x3 using minimal number of digits with one space separating each value */ printf(“Today’s temperature is %4.1d\n”, temp);

18. H. Huang Transparency No.4-18 The 68HC11 Microcontroller Rules for Conversion String -Between the % and the conversion character there may be, in order: 1.A minus sign, -- specify left adjustment. 2.A number that specifies the minimum field width. 3.A period that separates the field width from precision. 4.A number, the precision, that specifies the maximum number of characters to be printed from a string, or the number of digits after the decimal point, or the minimum of digits for an integer. 5. An h if the integer is to be printed as a short, or l (letter ell) if as a long.

19. H. Huang Transparency No.4-19 The 68HC11 Microcontroller Functions and Program Structure -Every C program consists of one or more functions. -Definition of a function cannot be embedded within another function. -A function will process information passed to it from the calling portion of the program, and return a single value. -Syntax of a function definition: return_type function_name (declarations of arguments) { declarations and statements } Example char lower2upper (char cx) { if cx > ‘a’ && cx <= ‘z’) return (cx - (‘a’ - ‘A’)); else return cx; }

20. H. Huang Transparency No.4-20 The 68HC11 Microcontroller Example 4.1 Write a function to test if an integer is a prime number. Solution: A number is a prime if it is indivisible by any integer between 2 and half of itself. /* this function returns a 1 if a is prime. Otherwise, it returns a 0. */ char test_prime (int a) { int i; if (a == 1) return 0; for (i = 2; i < a/2; i++) if ((a % i) == 0) return 0; return 1; } -A function must be defined before it can be called. -Function prototype declaration allows us to call a function before it is defined. -Syntax of a function prototype declaration: return_type function_name (declarations of arguments);

21. H. Huang Transparency No.4-21 The 68HC11 Microcontroller Example 4.2 Write a program to find out the number of prime numbers between 100 and 1000. Solution: #include char test_prime (int a);/* prototype declaration for the function test_prime */ main ( ) { inti, prime_count = 0; for (i = 100; i <= 1000; i++) { if (test_prime(i)) prime_count ++; } printf(“\n The total prime numbers between 100 and 1000 is %d\n”, prime_count); } char test_prime (int a) { int i; if (a == 1) return 0; for (i = 2; i < a/2; i++) if ((a % i) == 0) return 0; return 1; }

22. H. Huang Transparency No.4-22 The 68HC11 Microcontroller Pointers and Addresses -A pointer is a variable that holds the address of a variable. -Pointers provide a way to return multiple data items from a function via function arguments. -Pointers also permit references to other functions to be specified as arguments to a given function. -Syntax for pointer declaration: type_name *pointer_name; Examples int *ax; char *cp; -Use the dereferencing operator * to access the value pointed by a pointer. int a, *b; … a = *b;/* assigns the value pointed by b to a */

23. H. Huang Transparency No.4-23 The 68HC11 Microcontroller -Use the unary operator & to assign the address of a variable to a pointer. For example, int x, y; int *ip; ip = &x; y = *ip;/* y gets the value of x */

24. H. Huang Transparency No.4-24 The 68HC11 Microcontroller Example 4.3 Write a bubble sort function to sort an array of integers. Solution: void swap (int *, int *);/* function prototype declaration */ void bubble (int a[], int n)/* n is the array count */ { inti, j; for (i = 0; i < n - 1; i++) for (j = n - 1; j > i; j--) if (a[j - 1] > a[j]) swap (&a[j - 1], & a[j]); } void swap(int *px, int *py) { int temp; temp = *px; *px = *py; *py = temp; }

25. H. Huang Transparency No.4-25 The 68HC11 Microcontroller Arrays -An array consists of a sequence of data items that have common characteristics. -Each array is referred to by specifying the array name followed by one or more subscripts, with each subscript enclosed in brackets. Each subscript is a nonnegative integer. -The number of subscripts determines the dimensionality of the array. For example, x[i] is an element of an one-dimensional array y[i][j]refers to an element of a two-dimensional array -Syntax for one-dimensional array declaration: data-type array_name [expression]; -Syntax for two-dimensional array declaration: data-type array_name [expr1] [expr2];

26. H. Huang Transparency No.4-26 The 68HC11 Microcontroller Pointers and Arrays -Any operations that can be achieved by array subscripting can also be done with pointers. -The pointer version will in general be faster but, somewhat harder to understand. -For example, int ax[20];/* array of 20 integers */ int *ip;/* ip is an integer pointer */ ip = &ax[0]/* ip contains the address of ax[0] */ x = *ip;/* copy the contents of ax[0] into x. -If ip points to ax[0], then ip + 1 points to ax[1], and ip + i points to ax[i], etc.

27. H. Huang Transparency No.4-27 The 68HC11 Microcontroller Passing Arrays to a Function -An array name can be used as an argument to a function. -To pass an array to a function, the array name must appear by itself, without brackets or subscripts, as an actual argument within the function call. -When declaring a one-dimensional array as a formal argument, the array name is written with a pair of empty square brackets. -When declaring a two-dimensional array as a formal argument, the array name is written with two pairs of empty square brackets. -Example, int average (int n, int arr[ ]); main ( ) { int n, avg; int arr[50]; … avg = average (n, arr);/* function call with array name as an argument */ … } int average (int k, int brr [ ])/* function definition */ { … }

28. H. Huang Transparency No.4-28 The 68HC11 Microcontroller External Variables -A variable declared inside a function is called an internal variable. -A variable defined outside of a function is called a external variable. -An external variable is available to many functions. -External variables provide an alternative to function arguments and return values for communicating data between functions. -Any function may access an external variable by referring to it by name if the the name has been declared somewhere. Scope Rules -The functions and external variables that make up a C program can be compiled separately. -The source text of the program may be kept in several files. -The scope of a name is the part of the program within which the name can be used. -For a variable declared at the beginning of a function, the scope is the function in which the name is declared. -Local (internal) variables of the same name in different functions are unrelated. -The scope of an external variable or a function lasts from the point at which it is declared to the end of the file being compiled.

29. H. Huang Transparency No.4-29 The 68HC11 Microcontroller In the following program segmentThe use of external variables are illustrated in the following 2-file C program … in file 1 void f1 (…)extern int xy; {extern long arr [ ]; …main ( ) }{ … int a, b, c;} void f2(…)void foo (int abc) { … } {long soo (void) { … } … }in file 2 int xy; Variables a, b, and c are accessible tolong arr [100]; function f2 but not f1.

30. H. Huang Transparency No.4-30 The 68HC11 Microcontroller Using the ImageCraft C Compiler -An Integrated Development Software (IDS) may consist of a text editor, a compiler, a linker, a librarian, an assembler, a simulator, and debugger, etc. -An IDS uses project as the unit to control the software development. -A user creates C functions in one or multiple files using the editor provided by the integrated software. -The compiler is then invoked to compile each individual file. In most cases, you will need to eliminate syntax errors in this step. -Create a new project and add the files just created into this project. -Build the project. The IDS will combine all object modules into one executable module and may translate it into appropriate format suitable for downloading into a demo board for execution. -Download the module into a demo board for execution. -In the following, we will use a project that consists of a single file to illustrate the process of using the ImageCraft C compiler for program development:

31. H. Huang Transparency No.4-31 The 68HC11 Microcontroller Step 1. Invoke the ICC11 by clicking the icon of ICC1 program. A window appears as follows:

32. H. Huang Transparency No.4-32 The 68HC11 Microcontroller Step 2. Click the file menu and select new to create a new file for entering a new program. The screen look like this:

33. H. Huang Transparency No.4-33 The 68HC11 Microcontroller Step 3. Type in the new program and save it in an appropriate directory. An example is shown in Figure 4.3.

34. H. Huang Transparency No.4-34 The 68HC11 Microcontroller Step 4. Create a new project by clicking the project menu and select new. The screen is shown in Figure 4.4. After selecting new, the screen changes to Figure 4.5. After this, we need to enter the project name and the result is shown in Figure 4.6.

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36. H. Huang Transparency No.4-36 The 68HC11 Microcontroller

37. H. Huang Transparency No.4-37 The 68HC11 Microcontroller Step 5. Add the program to the newly created project. Press the Add button on Figure 4.6. A list of files will be displayed and you can select those files that you want to include in this project. Click on the file add.c and the result is shown in Figure 4.7.

38. H. Huang Transparency No.4-38 The 68HC11 Microcontroller Step 6. Setting appropriate options for the compiler, editor, and terminal program. The options available can be seen by pressing the Options menu shown in Figure 4.8.

39. H. Huang Transparency No.4-39 The 68HC11 Microcontroller Step 7. Set compiler preprocessor options. There are three sets of options that need to be set in the compiler: preprocessor, compiler, and linker. Select Compiler in Figure 4.8 and then click on Preprocessor and the screen shown in Figure 4.9a will be brought up. Enter the appropriate include path. Do not click on OK.

40. H. Huang Transparency No.4-40 The 68HC11 Microcontroller Step 8. Set compiler options. Click on the item compiler. The default options shown in Figure 4.9b are OK.

41. H. Huang Transparency No.4-41 The 68HC11 Microcontroller Step 9. Set linker options. Click the Linker button on Figure 4.9a to bring up the linker option screen. The appropriate option values for EVB demo board are shown in Figure 4.9c. The appropriate option values for CMD11A8 are shown in Figure 4.9d.

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43. H. Huang Transparency No.4-43 The 68HC11 Microcontroller Step 10. Set terminal options. Go back to Option menu and select Terminal. This will bring up the terminal option screen as shown in Figure 4.10. The com port can be com1 or com2. Baud rate should be set to 9600 for both EVB and CMD11A8. Flow control should be set to none. Font also need to set properly. A popular font is Courier or Courier New (shown in Figure 4.11). Click on OK and the screen will change back to Figure 4.8.

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45. H. Huang Transparency No.4-45 The 68HC11 Microcontroller Step 10. Build the project. Click the Build button and ICC11 will start to process your file. The Build button will be dimmed before it is done. When it is done, the Build button will change back to bold. Minimize both the project and source code windows and maximize the status window and the result is shown in Figure 4.12.

46. H. Huang Transparency No.4-46 The 68HC11 Microcontroller Step 11. Download the program onto the demo board for execution. Click the Target menu and select Terminal and this will bring up the terminal window as shown in Figure 4.13. Type load t followed by the enter key, and click on the Browse button. This would bring up a popup window (shown in Figure 4.14) for you to select a file to download. Select add.s19 and click OK button. Click the ASCII Download button to start downloading. The downloading process looks like that in Figure 4.15. A successful download should look like Figure 4.16.

47. H. Huang Transparency No.4-47 The 68HC11 Microcontroller Select a File to Download

48. H. Huang Transparency No.4-48 The 68HC11 Microcontroller Download Process

49. H. Huang Transparency No.4-49 The 68HC11 Microcontroller A Successful Download

50. H. Huang Transparency No.4-50 The 68HC11 Microcontroller Step 12. Program Execution and Debugging. ICC11 terminal program allows you to use all the Buffalo commands to debug the program when using an EVB and CMD11A8 demo board. Type G 2000 to run this program on the CMD11A8 demo board and the result would look like Figure 4.17. (Type G C000 on the EVB board).