1.           Define Relative based indexed addressing mode: 

      Relative Based Indexed Addressing Mode : Effective Address is calculated by the sum of 8- or 16 bit displacement and a based indexed address.

E.A.= (BX or BP) + (SI or DI) +( 8 bit displacement (sign extended ) or 16 bit displacement)

Physical Address= E.A + (DS)*16₁₀

2.           List the branch related addressing mode:

Intra segment Direct

Intra segment Indirect

Inter segment Direct

Inter Segment Indirect

3.           List the functions of Bus Interface Unit in 8086.

Sends out addresses

Fetches instructions from memory

Reads data from ports and memory

Writes data to port and memory

4.           Write any two advantages of segment registers in 8086

a.       It allows the memory capacity to be 1MB even though the address associated with individual instructions are 16 bits wide.

b.      It allows the instruction,data, or stack portion  of a program to be more than 64KB long by using more than one code, data, or stack segment

5.           What is the use of Instruction pointer in 8086 ?

Instruction pointer holds the 16 bit address of the next code byte within the code segment. The value contained in the IP is called effective address or offset. It contains the distance from the base address to the next instruction byte to be fetched.

6.           Write about the auxiliary carry flag used in 8086 ?

It is set if there is a carry out of bit 3 during an addition or a borrow by bit 3 during a subtraction. This flag is used exclusively for BCD arithmetic.

7.           When the Overflow flag is set ?

For addition of 16 bits, this flag is set when there is a carry into the MSB and no carry out of the MSB.

8.           Define Register addressing mode:

Datum is in the register that is specified by the instruction

E.g : MOV CX,AX          (16 bit operand)

        MOV CL,AL           ( 8 bit operand)

9.           Define Register Indirect Addressing mode:

Effective address of the datum is in the base register BX or an index register that is specified by the instruction.

10.      Define Register relative addressing mode:

The effective address is the sum of an 8- or 16 bit displacement and the contents of a base register or an index register.

11.      Define Based Indexed addressing mode:

The effective address is the sum of a base register and an index register , both of which are specified by the instruction.It is also called as Base related Indexed addressing.

12.      Define Intra segment direct addressing mode:

The effective branch address is the sum of an 8- or 16 bit displacement and the current contents of IP.

13.      Define Intra segment Indirect addressing mode:

The effective branch address is the contents of a register or memory location that is accessed using any of the data related addressing modes except the immediate mode. The contents of IP are replaced by the effective branch address.

14.      Define Inter segment addressing mode:

It replaces the contents of IP with part of the instruction and the contents of CS with another part of the instruction.

15.      Define Inter segment Indirect addressing mode:

It replaces the contents of IP and CS with the contents of two consecutive words in memory that are referenced by using any of the data related addressing modes except immediate and register modes.

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