Addressing modes in computer organization
- 1. COMPUTER ORGANISATION & ARCHITECTURE MEMORY ADDRESSING PART-2 SAJEENA SHAJI
- 2. Addressing Mode The different ways of specifying the location of an operand in an instruction are called as addressing modes. Elements of an instruction
- 3. ❏ Immediate Addressing mode ❏ Direct/ Absolute addressing mode ❏ Indirect addressing mode ❏ Register direct addressing mode ❏ Register indirect addressing mode ❏ Implicit addressing mode ❏ Stack addressing mode ❏ Displacement addressing mode ❏ Auto_increment addressing mode ❏ Auto_Decrement addressing Type of Addressing
- 4. Immediate Addressing Mode ● The operand is specified in the instruction explicitly. ● Instead of address field, an operand field is present that contains the operand. ● Example MOV R1,#100 LOAD R1,#10
- 5. Direct 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. ● Example MOV R1,1000
- 6. InDirect 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. ● Example MOV R1,(1000)
- 7. Register Direct 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. Example MOV R1, R2
- 8. Register InDirect 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. Example MOV R1, (R2)
- 9. Implied Addressing Mode ● The definition of the instruction itself specify the operands implicitly. ● It is also called as implicit addressing mode. Example PUSH, Complement Accumulator
- 10. Stack Addressing Mode ● The operand is contained at the top of the stack. ○ Example - ADD ● This instruction simply pops out two symbols contained at the top of the stack. ● The addition of those two operands is performed. ● The result so obtained after addition is pushed again at the top of the stack.
- 11. Displacement Addressing Mode ● Relative Addressing mode ● Base register Addressing mode ● Indexed Addressing mode
- 12. Relative Addressing mode Effective address of the operand is obtained by adding the content of program counter with the address part of the instruction.
- 13. Indexed Addressing mode Effective address of the operand is obtained by adding the content of index register with the address part of the instruction.
- 14. Base Register Addressing mode Effective address of the operand is obtained by adding the content of base register with the address part of the instruction.
- 15. Auto Increment Addressing mode ● After accessing the operand, the content of the register is automatically incremented by step size ‘d’. ● Step size ‘d’ depends on the size of operand accessed. ● Only one reference to memory is required to fetch the operand.
- 17. Auto decrement Addressing mode ● First, the content of the register is decremented by step size ‘d’. ● Step size ‘d’ depends on the size of operand accessed. ● After decrementing, the operand is read. ● Only one reference to memory is required to fetch the operand.
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