INTRODUCTION TO MICROPROCESSOR

Engr. Ammar Anwar Khan

TUTORIAL # 2 EE-353

Physical and Logical Addresses

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8086 MICROPROCESSOR

MEMORY

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INSTRUCTION - MOV

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MOV AX, BX

Mneunomincs

Move => MOV

Addition => ADD

Operands – Source, Destination

AX, BX etc or may be zero operand (e.g., HLT=> halt)

SEGMENT REGISTERS

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ADDRESSES

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8086 addresses are specified as xxxx:yyyy

where xxxx is value in segment register

yyyy is offset

Addresses are specified as relative to start of segment

eg. Instruction Pointer relative to Code Segment

EXAMPLES

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Logical Address

CS:IP, DS:IP, ES:IP, SS:SP

3000:1500

Physical Address (20 bits)

Shift Left CS, DS,ES or SS; 30000

Add the result to IP or SP

30000+1500=31500 is the Physical Address.

EXAMPLES

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If CS=3000 and IP=1500

Offset =1500

Logical Address =3000:1500

Physical Address =31500

Lower range =30000+0000=30000

Upper Range = 30000+FFFF=3FFFF

EXAMPLES

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If SS=3500 and SP=FFEE

Offset =FFFE

Logical Address =3500:FFFE

Physical Address =44FFE

Lower range =35000+0000=35000

Upper Range = 35000+FFFF=44FFF

STACK MEMORY

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SS and SP

Used to store value on the RUN

PUSH => to store the value in the memory

POP => Take out the value from the memory

PUSH AX

POP AX

STACK MEMORY

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STACK MEMORY

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LITTLE ENDIAN

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Higher byte goes to Upper address

Lower byte goes to Lower address

MOV AX,6545

MOV [1500], AX

[1500] = 45

[1501] = 65

Same for stack !!!!!

FLAG REGISTER

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DEBUG- COMMAND PROMPT

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DEBUG- COMMAND PROMPT

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DEBUG- COMMAND PROMPT

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DEBUG- COMMAND PROMPT

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DEBUG- COMMAND PROMPT

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End

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