CPE317 Microprocessor (Part 2) PDF

**CPE317 MICROPROCESSOR (part 2)** - **ASSEMBLY LANGUAGE:** Low-level programming language for microprocessors and other devices.\ Basic programming language for processors.\ Processors understand machine language instructions. - **COMPILATION FLOW:** - ***C/C++ Compi...

**CPE317 MICROPROCESSOR (part 2)** - **ASSEMBLY LANGUAGE:** Low-level programming language for microprocessors and other devices.\ Basic programming language for processors.\ Processors understand machine language instructions. - **COMPILATION FLOW:** - ***C/C++ Compilation Process***:\ \ **[Preprocessing:]** Processes include-files, conditional compilation instructions, and macros.\ **[Compilation:]** Takes preprocessor output and source code, generates assembler source code.\ **[Assembly:]** Produces assembly listing with offsets from assembly source code.\ **[Linking:]** Combines object files or libraries to produce a single file. - **MACHINE LANGUAGE --** z=x+y  - **MACHINE & ASSEMBLY LANGUAGE:** - ***Assembly Language Overview:\ *** Uses symbolic names for operations, registers, memory locations.\ Higher-level language with better instructions readability.\ Provides one-to-one correspondence with machine language instructions. - **[Assemblers]** translate assembly to machine code - **[Compilers]** translate high-level programs to machine code, either directly or indirectly, via an assembler - **ASSEMBLER** - An assembler is a program that converts source-code programs written in assembly language into object files in machine language. - TASM (Turbo Assembler from Borland) - MASM (Microsoft Macro Assembler) - NASM (Netwide Assembler for both Windows and Linux), and - GNU assembler distributed by the free software Foundation - **MNEMONICS --** MOV AX, BX Specify opcode for complete machine language instruction.\ Assembler translates to generate object code.\ MOV used for data copy/movement between registers/memory locations. - **INSTRUCTION:**\ Program commands i***nstructions*** computer actions.\ Computers handle binary data; hence instructions must be in binary format (0s, 1s).\ All binary instructions form the computer\'s ***machine language***, also known as the ***instruction set***. - **INTRUCTION FIELDS:** - Opcode field specifies specific operation. - Each operation has unique opcode. - Operands fields specify source and destination operands. - Source/destination can be constant, memory, or general-purpose registers. - **ASSEMBLY INSTRUCTION --** Built from two pieces  - **TYPES OF OPCODES:** - ***Arithmetic & Logical*** ADD, SUB, MULT, AND, OR, CMP - ***Memory Load/Store*** LOAD, LD, LOD, ST - ***Control Transfer*** JMP, BNE - ***Complex*** MOVS - **ASCII:** Scheme for assigning numeric values to punctuation marks, spaces, numbers, etc.\ Uses 7 bits for character representation.\ Uses values 0000000-1111111 or 00-7F for 128 characters.\ Extended version assigns characters from 80-FF. - **PARTS OF ASSEMBLY LANGUAGE PROGRAM:** - Header Files - Directives - Labels - Comments - **ASSEMBLY LANGUAGE: HEADER FILES** No direct concept of header files.\ Used to define functions, variables, macros.\ Can be included in multiple source files. - **MACROS:** Defined using ***.macro*** and ***.endm*** directives.\ Useful for defining reusable code blocks.\ Can take parameters and be expanded inline during assembly. 1. **INCLUDE:** Supports ***.include*** for file inclusion.\ Facilitates sharing of common definitions or code snippets. 2. **EXTERNAL REFERENCE:** Declareable using ***.extern*** directive.\ Symbols can be in assembly files or C/C++ code.\ Linker resolves external references during linking process. 3. **Org 100h:** Specific to MASM and TASM.\ Sets code segment origin.\ Involves org 100h, instructing assembler to place instructions at memory address 100h. 4. **include 'emu8086.inc':\ ** Includes emu8086.inc file for EMU8086 environment definitions.\ Provides macro functions for IO, mathematic operations**.** - **DIRECTIVES:** Commands for controlling assembly process.\ Guide assembler in interpreting and translating assembly code. 1. **DATA DEFINITION DIRECTIVES:** A. **[DB/db] -** This data definition directive defines bytes of data. Example: message DB \'Hello, world!\', 13, 10, '\$' message db 'Hello, world!', 13, 10, '\$' B. **[DW/dw -]** This data definition directive defines words of data. Example: number DW 1234h number dw 1234h C. DD/dd - This data definition directive defines doublewords of data. Example: dword\_value DD 12345678h dword\_value dd 12345678h D. **DQ/dq -** This data definition directive defines quadwords of data. Example: qword\_value DQ 123456789ABCDEF0h qword\_value dq 123456789ABCDEF0h 2. **SEGMENT DEFINITION DIRECTIVES:** A. **.data -** This segment definition directive defines the data segment.  B. **.code -** This segment definition directive defines the code segment. C. **.bss -** EMU8086 Assembly: Segment Definition Directive\ Defines initialized data segment.\ Doesn\'t support this directive.\ Uses.data directive. - **OTHER DIRECTIVES:** *\*\* These directives are not directly supported in the EMU8086 assembler. \*\** - ***.align:*** Aligns the next data or instruction to a specified boundary. - ***.byte:*** Defines a byte-sized value. - ***.word:*** Defines a word-sized value. - ***.long:*** Defines a long word-sized value. - **MEMORY MODEL:** Organize and manage memory segments for code, data, and stack.\ Crucial in older 16-bit x86 architectures.\ Ensured limited and segmented memory. - *Here is the list of common memory model stacks used in* *Assembly Language:* a. Small Model b. Medium Model c. Compact Model d. Large Model e. Huge Model A. **SMALL MODEL:** Specifics 64KB code and data segments.\ Ideal for small programs. B. **MEDIUM MODEL:** Code segments up to 1MB.\ Data segments limit to 64KB each. C. **COMPACT MODEL:** Data segments up to 1MB.\ Code segments limit to 64KB each. D. **LARGER MODEL:** Specifies memory model.\ Can hold up to 1MB code/data segments. E. **HUGE MODEL:** Specifies memory model.\ Can accommodate up to 4GB code/data segments. - **KEY POINTS OF MEMORY MODELS:** - Memory Model Impact on Program\ Affects addressing modes and instructions.\ Choice impacts performance and code size.\ Limitations exist, especially for larger programs. - **LABELS:** Symbolic names for memory locations.\ Mark jump instructions target.\ Define entry procedure.\ Reference data locations. - **COMMENTS -** Comments are supplementary text added to the code to enhance comprehension, but they are typically ignored by the assembler. - **BEST PRACTICE FOR USING LABELS & COMMENTS:** a. ***Clear and Concise Labels:*** Use meaningful labels that reflect the purpose of the code. b. ***Consistent Formatting:*** Use consistent indentation and spacing to improve readability. c. ***Explain Non-Obvious Code:*** Comment on complex or tricky parts of the code. d. ***Use Comments to Describe the Overall Purpose of a Code Section.*** e. ***Avoid Over-Commenting:*** Too many comments can clutter the code. f. ***Update Comments as Code Changes:*** Ensure comments remain accurate. - **CONTROL FLOW INSTRUCTION -** Control flow instructions are used to alter the normal sequential execution of instructions. Here are some common control flow instructions: a. Unconditional Jump b. Conditional Jump c. Looping d. Procedures and Subroutines - **UNCONDITIONAL JUMP:** Fundamental control flow mechanism.\ Allows abrupt program execution transfer.\ Doesn\'t meet specific condition.\ Defined as \"unconditional.\" - **CONDITONAL JUMP:** Instruction altering program\'s control flow.\ Condition evaluated through value comparison or processor flag status check. - ***Conditional Jumps instruction:*** a. **[JZ label:]** Jump if zero b. **[JNZ label]**: Jump if not zero c. **[JA label:]** Jump if 1st operand is above the 2nd d. **[JB label:]** Jump if 1st operand is below the 2nd e. **[JE label:]** Jump if 1st operand is equal to the 2nd f. **[JNE label]**: Jump if 1st operand is not equal to the 2nd g. **[JG:]** Jump inf 1st operand is greater than the 2nd h. **[JL:]** Jump if the 1st operand is less than the 2^nd^ - **LOOPING:** Executes code block repeatedly until condition is met.\ Combines conditional jumps and instruction counters. a. ***Loop instruction*** automatically decrements CX register and jumps back to label if CX isn\'t zero. b. ***Conditional jump (JLE)*** checks if condition is met, jumps back to loop start if necessary. - **PROCEDURES & SUBROUTINES:** Facilitates modularity.\ Enhances code reusability.\ Improves program organization. a. ***Procedures:*** Sequence of instructions for specific tasks. b. ***Subroutines:*** Smaller, specialized tasks for multiple locations.