Addressing Modes for engineering students of under-graduation program

1. Computer
Architecture
TOPIC: ADDRESSING MODES

2. The different ways of specifying the
location of an operand in an instruction
are called as addressing modes.
ADDRESSING MODE

3. TYPES OF ADDRESSING MODES
Immediate01
Direct02
Indirect03
Register04
Register indirect05
Displacement06
Stack07
Addressing
modes

4. In this addressing mode,
• The operand is specified in the
instruction explicitly.
• Instead of address field, an
operand field is present that
contains the operand.
IMMEDIATE ADDRESSING MODE

5. In this addressing mode,
• The address field of the instruction
contains the effective address of
the operand.
• Only one reference to memory is
required to fetch the operand.
• It is also called as absolute
addressing mode.
DIRECT ADDRESSING MODE

6. In this addressing mode,
• The address field of the instruction
specifies the address of memory
location that contains the effective
address of the operand.
• Two references to memory are
required to fetch the operand.
INDIRECT ADDRESSING MODE

7. In this addressing mode,
• The operand is contained in a
register set.
• The address field of the instruction
refers to a CPU register that contains
the operand.
• No reference to memory is required
to fetch the operand.
REGISTER ADDRESSING MODE

8. In this addressing mode,
• The address field of the instruction
refers to a CPU register that
contains the effective address of the
operand.
• Only one reference to memory is
required to fetch the operand.
REGISTER INDIRECT ADDRESSING MODE

9. In this addressing mode,
• Effective address of the
operand is obtained by
adding the content of index
register with the address part
of the instruction.
DISPLACEMENT ADDRESSING MODE

10. In this addressing mode,
• The operand is contained
at the top of the stack.
STACK ADDRESSING MODE

11. ADDRESS CALCULATION PERFORMED FOR EACH ADDRESSING MODE
Virtually all computer architectures provide more than one of these addressing modes.
Often, different opcodes will use different addressing modes. Also, one or more bits in
the instruction format can be used as a mode field. The value of the mode field
determines which addressing mode is to be used.
The second comment concerns the interpretation of the effective address (EA). In a
system without virtual memory, the effective address will be either a main memory
address or a register. In a virtual memory system, the effective address is a virtual
address or a register. The actual mapping to a physical address is a function of the
memory management unit (MMU) and is invisible to the programmer.

12. PREPARED BY:
Ankon Gopal Banik
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