Question

what are the different addressing modes used in unconditional branch/ jump instructions? Illustrate how the new program counter value is calculated in each case.

Answer 1

Solution: Some of the addressing modes that are widely used in while executing the jump instructions are:

1. Intersegment Direct Mode: In this mode of addressing the control can be sent from one segment of the program to another, it helps in branching from one code segment to another within the code. In this, the addresses are specified directly. For example, JMP 7000H, 1000H; it helps the control to jump to effective address 1000H in segment 7000H.
2. Intersegment Indirect Mode: In this mode of addressing, the control is actually transferred to a different code segment but the only difference is that the address is passed to the instruction in this case indirectly and it basically contains four bytes that are IP(LSB), IP(MSB), CS(LSB) and CS(MSB) sequentially.
3. Intrasegment Direct Mode: In this addressing mode the destination address to which the control is supposed to be transferred actually lies within the same segment and in this mode, the displacement is always computed relative to the content of the instruction pointer. For example, JMP SHORT LEVEL.
4. Intrasegment Indirect Mode: In this mode, the displacement is actually transferred to the instruction indirectly and with the help of this mode, the control can be transferred to the destination address within the same segment. For example, JMP [SX]; It makes the control to jump to the effective address stored in register SX.

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