EcE 3015 MICROPROCESSOR

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EcE 3015MICROPROCESSOR

• B.Tech. (First Year)
• Electronic Engineering

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Software Model of the 8088 Microprocessor

• Instruction Pointer (IP)
• Data Registers (AX,BX,CX, DX)
• Pointer Registers( BP,SP)
• Index Registers (SI,DI)
• Segment Registers (CS,SS, DS,ES)
• Status Register

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Instruction Pointer

• 16 bit register
• Offset of the next instruction

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General Purpose Data Registers

• Four nos. of 16 bit registers
• Accumulator (A), Base regiser (B), Count register
  (C), Data register (D)

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Pointer and Index Registers

• Two nos. of 16 bit pointer registers (SP, BP)
• Two nos. of 16 bit index registers (SI, DI)

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SP and BP

• Use for the offset from the current value of SS .

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SI and DI

• Hold the offset address of data stored in the
  data segment of memory
• Use indexed addressing

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Status Register

• 6 bits represent status flags.
• 3 bits are control flags.

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Memory Segmentation

• Code Segment
• Stack Segment
• Data Segment
• Extra Segment

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Memory
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Address Calculation

• Base Address 0000
• Offset address 0004

Base Address 0000 Offset address 0004
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Address Calculation
Base Address 1000 Offset address 0004
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Address Calculation
Base Address 2000 Offset address 0004
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• Segment Base address is stored in Segment
  register.
• Code segment base address CS
• Stack segment base address SS
• Data segment base address DS
• Extra segment base address ES

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Addressing Modes

• Register Addressing
• Immediate Addressing
• Direct Addressing
• Register Indirect Addressing
• Based Addressing
• Indexed Addressing
• Based Indexed Addressing
• String Addressing
• Port Addressing

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Register Addressing

• MOV AX, BX

Before executing the instruction,
After executing the instruction,
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Immediate Addressing
MOV AL, 15
Before executing the instruction,
After executing the instruction,
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Direct Addressing
MOV CX, BETA
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Register Indirect Addressing
MOV AX, SI
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Based Addressing
MOV BXBETA,AL
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Indexed Addressing
MOV AL, SIARRAY
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Based Indexed Addressing
MOV AH, BXSIBETA
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String Addressing

• MOVS

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Port Addressing

• For direct addressing,
• IN AL, 15H

For indirect addressing, IN AL, DX
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Instruction Format
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Instruction Set

• Data transfer instruction
• Arithmetic instruction
• Logic instruction
• Shift
• Rotate
• Flag control
• Compare
• Jump
• Subroutine
• Loop
• String

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Development of a program

• Create a source program, test.asm,
• using editor
• tasm test.asm
• tlink test.obj
• test.exe