10. PA = SBR or (SR) : EA
= : + +
The Operand resides
in an internal Register.
Examples:
AND AL,DH
AND BX,CX
The Operand is a part
of the Instruction.
Examples:
AND AL,80h
AND 0800h,BX
Direct Add.
Register
indirect Add.
Based Add.
Indexed Add.
Based
Indexed Add.
CS
DS
ES
SS
BX
BP
SI
DI
8-BIT or
16-BIT Displacement
It is a method for specifying an Operand
11. 1. Direct Addressing Mode
PA = SBR or (SR) : EA
= : + +
CS
DS
ES
SS
BX
BP
SI
DI
8-BIT or
16-BIT Displacement
= :
CS
DS
ES
SS
Direct Address
Examples:
AND AL,[1234h]
AND CX,[0FEDBh]
AND BL,ES:[52DBh]
13. 2. Register Indirect Addressing Mode
PA = SBR or (SR) : EA
= : + +
CS
DS
ES
SS
SI
DI
8-BIT or
16-BIT Displacement
= :
CS
DS
ES
SS
Examples:
AND AL,[SI]
AND CX,[DI]
AND BL,ES:[BX]
BX
BP
SI
DI
15. 3. Based Addressing Mode
PA = SBR or (SR) : EA
= : + +
CS
DS
ES
SS
BX
BP
SI
DI
8-BIT or
16-BIT Displacement
Examples:
AND AL,[BX]+1234h
AND CX,[BP] [1234]
AND BL,ES:[BX+12FEh]
= : +
CS
DS
ES
SS
BX
BP
8-BIT or
16-BIT Displacement
17. 4. Indexed Addressing Mode
PA = SBR or (SR) : EA
= : + +
CS
DS
ES
SS
BX
BP
SI
DI
8-BIT or
16-BIT Displacement
= : +
CS
DS
ES
SS
Examples:
AND AL,[SI] [50]
AND CX,[SI] [1234h]
AND BL,ES:[DI+12FEh]
DI
SI
8-BIT or
16-BIT Displacement
19. 5. Based Indexed Addressing Mode
PA = SBR or (SR) : EA
= : + +
CS
DS
ES
SS
BX
BP
SI
DI
8-BIT or
16-BIT Displacement
Examples:
AND AL,[SI]+[BX]+[1234h]
AND CX,[DI] [BP] [1234h]
AND BL,CS:[BX+DI+12FEh]
23. 16 – bit 2 Bytes
Lower Byte D0 –D7
Upper Byte D8 –D15
Used to transfer DATA between CPU
and Memory.
24. 20 – bit
One way BUS from CPU to Memory
Addresses up to 1M Byte of Memory
Generated by CPU to locate a specific Byte or Word in Memory
Physical Address (PA) : Physical Byte address in Memory
Effective Address (EA) : a number added to Segment Register
contents and gives PA
Segment Register is either CS, DS, ES or SS
i.e. : PA(20-bit) = SR(16-bit) + EA(16-bit)
25. Digital signals generated either by CPU or
by other Supporting ICs
They manages the whole CPU operations
Some of them called Control signals, the
others called Status signals
Control signals direction is from CPU
to Memory and other Supporting ICs.
Status signals direction is from
Supporting ICs to CPU.
