Executing Computer Instructions in 8086

Executing Computer Instructions in 8086 - Executing...

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1 CS 3401 Comp. Org. & Assembly Executing Computer Instructions in 8086 1 Executing Computer Executing Computer Instructions Instructions CS 3401 Comp. Org. & Assembly Executing Computer Instructions in 8086 2 Objective Objective DEBUG Program DEBUG Commands Rules of DEBUG Commands DEBUG Display Viewing Memory Locations Machine and Assembly Language Keying in program instructions and data Execute program instructions CS 3401 Comp. Org. & Assembly Executing Computer Instructions in 8086 3 Map of the First MB of Memory Map of the First MB of Memory Interrupt Vector Table Dos Data Area Software BIOS Dos Kernel Device Drivers Resident part of COMMAND.COM Transient part of COMMAND.COM Video Graphics Buffer MDA Text Buffer Color Text Buffer Reserved ROM BIOS Address 0000 0040 9FFF A000 B000 B800 C000 F000 FFFF Available RAM for transient programs 640K RAM CS 3401 Comp. Org. & Assembly Executing Computer Instructions in 8086 4 Registers Registers High-speed storage directly inside the CPU (CPU has internal data bus that is twice as wide as external data bus) Segment registers Pointer registers General-purpose registers Index registers Flags register
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2 CS 3401 Comp. Org. & Assembly Executing Computer Instructions in 8086 5 Segment Registers Segment Registers Used as base locations (addresses) for program instructions, data, and stack CS (code segment) -- holds the base location for all executable instruction (code) in a program DS (data segment) -- default base location for variables SS (stack segment) -- holds the stack base location ES (extra segment) -- additional base location CS 3401 Comp. Org. & Assembly Executing Computer Instructions in 8086 6 Pointer Registers Pointer Registers Contain the offsets of data instructions IP (instruction pointer) contains the offset address of the next instruction to be executed associated with CS register BP (base pointer) contains an assumed offset from SS register used by subroutine to locate variables SP (stack pointer) contains the offset of the top of the stack SS and SP combine to form a complete address CS 3401 Comp. Org. & Assembly Executing Computer Instructions in 8086 7 Instruction Pointer Register Instruction Pointer Register Segment address in CS 39B40h Offset address in IP +514h Address of next instruction 3A054h CS 3401 Comp. Org. & Assembly Executing Computer Instructions in 8086 8 General Purpose Registers General Purpose Registers Data registers -- used for arithmetic and data movement can be addressed as either an 8-bit or a 16-bit AX (accumulator) -- arithmetic operations
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Executing Computer Instructions in 8086 - Executing...

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