Prerequisite – Addressing Modes
1. Register Mode :
In register addressing mode, the operand is placed in one of 8 bit or 16 bit general purpose register. The data is in the register that is specified by the instruction.
MOV R1, R2
Instruction has register R2 and R2 has operand.
2. Register Indirect Mode :
In register indirect addressing mode, the address of operand is placed in any one of the registers. The instruction specifies a register that contains the address of the operand.
ADD R1, (R2)
Instruction has register R2 and R2 has memory address of operand.
Difference between Register Mode and Register Indirect Mode :
|REGISTER MODE||REGISTER INDIRECT MODE|
|Operand is placed in general purpose register.||Operand’s offset is placed in one of the resgiters.|
|In register mode, address field contains the effective address of operand.||In register indirect mode, address field contains reference of effective address.|
|It requires only one register reference to access data.||It requires two register references to access data.|
|No further calculation is required to perform the operation.||Require further calculation to find the effective address.|
|Register addressing mode is fast.||register indirect addressing mode is slow.|
|It is easier to access the data in register mode.||It is a bit complex to access the data in register indirect mode.|
|It uses temporary variables.||It uses pointers.|
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