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ESE350: Introduction to Embedded Systems MC9S12C128 C Assembly Language Structure Lecture 3

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ESE350: Introduction to Embedded Systems MC9S12C128 C Assembly Language Structure Lecture 3

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    1. ESE350: Introduction to Embedded Systems MC9S12C128 C & Assembly Language Structure Lecture #3 Professor Rahul Mangharam Electrical and Systems Engineering University of Pennsylvania

    2. Outline of Today’s Lecture From C to Assembly Bitwise Operators Parts of an Assembly Program Putting it altogether 2

    3. From C to Assembly 3

    4. Machine Code Machine instructions: A sequence of binary digits which can be executed by the processor 0001 1000 0000 0110: [A] + [B] -> A ABA 01000011: [A]+1->A INCA 1000 0110 0000 0110: 6 -> A LDA #06 Unless you are Neo…. Hard to understand, enter, debug, and maintain for human being A readable equivalent of what is performed is shown first A mnemonic for the machine instruction is shown second. 4

    5. Machine/Assembly Code Example The example shows: The address where the machine code is to be stored in memory The machine code in hex The assembly code or source code with an assembler directive The assembler directive tells the assembler at what address to start storing the machine code 5

    6. Assembly Language Defined by assembly instructions An assembly instruction is a mnemonic representation of a machine instruction Mnemonic What it does; ABA [A]+[B]->A ; DECA [A]-1->A Assembly programs must be translated into machine instructions before it can be executed -- translated by an assembler There are two kinds of assemblers: native assembler and cross assembler Programmers need to work on the program logic at a very low level and cannot achieve high productivity. 6

    7. Assembly Language Example Ldx #Array1 ;Loads index register X with start address of Array1 Ldy #Array2 ;Loads index register Y with start address of Array2 Ldab #$0A ;Loads B accumulator with value 10 for counter 7

    8. High-level Language Syntax of a high-level language is similar to English. A translator is required to translate the program written in a high-level language -- done by a compiler. There are two types of compilers: native compiler and cross compiler. High-level languages allow the user to work on the program logic at higher level and achieve higher productivity. Source code A program written in assembly or high-level language Object code The output of an assembler or compiler 8

    9. Let us C… C has gradually replaced assembly language in many embedded applications. A summary of C language constructs that will be used in HCS12 programming. Books on C language Kernighan & Ritchie, “The C Programming Language”, Prentice Hall, 1988. Deitel & Deitel, “C: How to Program”, Prentice Hall, 1998. –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: Declaration Assignment Function call Control Null A variable stores a value to be used during the computation. The main () function is required in every C program. 9

    10. C Data Types for Microcontrollers 10

    11. Bitwise Operators (1) 11

    12. Bitwise Operators (1) 12

    13. Relational and Logical Operators (1) 13

    14. Relational and Logical Operators (2) 14

    15. Parts of an Assembly Program 15

    16. Assembly Directives 16

    17. Other Directives 17

    18. Parts of Assembly Instruction 18

    19. An Assembly Instruction 19

    20. Instruction Classifications 20

    21. Other Instruction Classifications 21

    22. Some Assembly Instructions 22

    23. 23

    24. 24

    25. 25

    26. Addressing Modes 26

    27. Extended Addressing 27

    28. Direct Addressing 28

    29. Immediate Addressing 29

    30. Indexed Addressing 30

    31. Inherent & Relative Addressing 31

    32. Instruction Execution Cycle 32

    33. 33

    34. 34

    35. 35

    36. Putting it altogether - An Assembly Program 36

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