Intel Instruction Set Architecture

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Intel Instruction Set Architecture

• Basic PC Hardware
• Instruction Addressing and Execution
• Using DEBUG to examine computer memory and
  instruction execution

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Basic Features of PC Hardware

• Bits and Bytes
• bit smallest unit of storage of binary value
  (0 or 1)
• byte 8-bit storage
• Word two bytes
• Double word two words, four bytes
• Paragraph 16 bytes
• Binary Number Systems
• Definition
• Binary arithmetic
• Twos compliment for negative numbers
• Addition and subtraction

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• Hexadecimal Representation
• 4 bits to represent a single hexadecimal digit
  0, 1, , 9, A, B, C, D, E, F.
• Conversions between binary and hexadecimal
  numbers
• ASCII Code
• 8 bits to represent a ASCII (American Standard
  Code for Information Exchange) characters
• 256 of them
• Some are not printable
• Letter A 01000001 41H

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• PC components
• CPU
• Main Memory
• Input/Output Devices
• Intel CPU (Int-Fig 2-1)
• Data registers
• Accumulators AX (AH, AL), EAX
• Base Index BX (BH, BL), EBX
• Count CX(CH, CL), ECX
• Data DX(DH, DL), EDX

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• Control Registers
• Instruction Pointer IP, EIP
• Flags FLAGS, EFLAGS
• Segment Registers
• Code CS (16-bit)
• Data DS (16-bit)
• Stack SS (16-bit)
• Extra ES (16-bit)
• Special Registers
• Stack Pointer SP, ESP
• Base Pointer BP, EBP
• Destination Index DI, EDI
• Source Index SI, ESI

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• Memory
• Sequence of locations to store instruction and
  data
• Each byte has an address.
• An address is a binary number which specifies the
  corresponding byte uniquely.
• Alignment of multi-byte data in memory
• Addressing multi-byte data in memory
• Little ending ---- uses the address of the least
  significant byte as the address of the whole data
• Big ending --- uses the address of the most
  significant byte as the address of the whole data
• Intel is a little ending machine.

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• Segmentation
• Each program has
• Code section for the instructions
• Data section the global static data
• Stack section for the storage
• To save registers
• The stack frames for the local variables of the
  function (routine) called
• Each section is addressed by using
• The segment address
• Offset with the segment
• Code Segment CS IP
• Stack Segment SS SP
• Data Segment DS Offset

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