Micro computing Systems

Content	Link
Module 1	Module 1- 8086 Notes
Module 1	8086 -Memory management -notes
Module 1	8086 Architecture -Power point
Module 1	8086 Instruction set and addressing mode -PPT
Module 1	ARM processor PPT
Module 1	ARM processor PPT
Module 2	8051 Controller ppt
Module 2	8051 Controller ppt
Queastion Bank	Question bank CIA 1
Queastion Bank	Question bank CIA 1 Part A Answer

Assending order of ALP model of 8086 processor

  ORG 100h        ; Origin at 100h

MOV SI, OFFSET NUMBERS ; SI points to the array of numbers
MOV CX, 5       ; Number of elements to sort (change as needed)

SORT_LOOP:
    MOV BX, CX      ; Inner loop counter
    DEC BX          ; Decrement BX since we compare BX with BX+1

INNER_LOOP:
    MOV AX, [SI]    ; Load the value at SI into AX
    CMP AX, [SI+2]  ; Compare with the next value
    JLE NO_SWAP     ; Jump if less than or equal (no swap needed)

    ; Swap the values
    XCHG AX, [SI+2]
    MOV [SI], AX

NO_SWAP:
    ADD SI, 2       ; Move to the next element
    LOOP INNER_LOOP ; Repeat for all elements

    DEC CX          ; Decrement outer loop counter
    LOOP SORT_LOOP  ; Repeat for all elements

   

NUMBERS DB 23, 11, 56, 7, 34 ; Array of numbers to sort

END
  

unit III- Q&A -2 marks -Digital System Design Through VHDL -R19 ECE JNTUA

ADDRESSING MODES OF 8086

ADDRESSING MODES OF 8086

Sequential control flow instructions. 1

1.     Immediate: 2

2.     Direct 2

3.     Register 2

4.     Register Indirect 2

5.     Indexed. 2

6.     Register Relative. 3

7.     Based Indexed. 3

8.     Relative Based Indexed. 3

The control transfer instructions: 3

9.     Intra-segment direct mode: 4

10         Intra-segment Indirect Mode. 4

11. Inter-segment Direct Mode: 5

12.Inter-segment Indirect Mode: 5

Addressing mode indicates a way of locating data or operands. Depending upon the data types used in the instruction and the memory addressing modes, any instruction may belong to one or more addressing modes, or some instruction may not belong to any of the addressing modes. Thus the addressing modes describe the types of operands and the way they are accessed for executing an instruction. Here, we will present the addressing modes of the instructions depending upon their types.

 According to the flow of instruction execution, the instructions may be categorized as

(i)                 Sequential control flow instructions and

(ii)               Control transfer instructions.

Sequential control flow instructions are the instructions, which after execution, transfer control to the next instruction appearing immediately after it (in the sequence) in the program. For example, the arithmetic, logical, data transfer and processor control instructions are sequential control flow instructions.

1. Immediate: In this type of addressing, immediate data is a part of instruction, and appears in the form of successive byte or bytes.

Example: MOV AX, 0005H

In the above example, 0005H is the immediate data. The immediate data may be 8-bit or 16-bit in size.

2. Direct: In the direct addressing mode, a 16-bit memory address (offset) is directly specified in the instruction as a part of it.

Example: MOV AX, [5000H]

Here, data resides in a memory location in the data segment, whose Physical address may be computed using 5000H as the offset address and content of DS as segment address. The Physical address, here, is 10H*DS+5000H.

3. Register: In register addressing mode, the data is stored in a register and it is referred using the particular register. All the registers, except IP, may be used in this mode.

Example: MOV BX, AX.

4. Register Indirect: Sometimes, the address of the memory location, which contains data or operand, is determined in an indirect way, using the offset registers. This mode of addressing is known as register indirect mode.

In this addressing mode, the offset address of data is in either BX or SI or DI registers. The default segment is either DS or ES. The data is supposed to be available at the address pointed to by the content of any of the above registers in the default data segment.

Example: MOV AX, [BX]

Here, data is present in a memory location in DS whose offset address is in BX. The Physical address of the data is given as 10H*DS+ [BX].

5. Indexed: In this addressing mode, offset of the operand is stored in one of the index registers. DS and ES are the default segments for index registers SI and DI respectively. This mode is a special case of the above discussed register indirect addressing mode.

Example: MOV AX, [SI]

Here, data is available at an offset address stored in SI in DS. The Physical address, in this case, is computed as 10H*DS+ [SI].

6. Register Relative: In this addressing mode, the data is available at an Physical address formed by adding an 8-bit or 16-bit displacement with the content of any one of the registers BX, BP, SI and DI in the default (either DS or ES) segment. The example given before explains this mode.

       Example: MOV Ax, 50H [BX]

       Here, Physical address is given as 10H*DS+50H+ [BX].

7. Based Indexed: The Physical address of data is formed, in this addressing mode, by adding content of a base register (any one of BX or BP) to the content of an index register (any one of SI or DI). The default segment register may be ES or DS.

Example: MOV AX, [BX] [SI]

Here, BX is the base register and SI is the index register. The Physical address is computed as 10H*DS+ [BX] + [SI].

8. Relative Based Indexed: The Physical address is formed by adding an 8-bit or 16-bit displacement with the sum of contents of any one of the bases registers (BX or BP) and any one of the index registers, in a default segment.

Example: MOV AX, 50H [BX] [SI]

Here, 50H is an immediate displacement, BX is a base register and SI is an index register. The Physical address of data is computed as 160H*DS+ [BX] + [SI] + 50H.

The control transfer instructions:

 The addressing modes depend upon whether the destination location is within the same segment or a different one. It also depends upon the method of passing the destination address to the processor.

Basically, there are two addressing modes for the control transfer instructions, viz. inter-segment and intra-segment addressing modes.

If the location to which the control is to be transferred lies in a different segment other than the current one, the mode is called inter-segment mode. If the destination location lies in the same segment, the mode is called intra-segment.

Inter-segment Direct

                                         

                                                         Inter-segment

                                                                                               Inter-segment

                                                                                                Indirect

Modes for control

Transfer instructions

                                                                                               Intra-segment

                                                        Intra-segment                 Direct

                                                                 

                                                                                                     Intra-segment

                                                                                                      Indirect                      

Addressing Modes for Control Transfer Instruction

9.      Intra-segment direct mode:

In this mode, the address to which the control is to be transferred lies in the same segment in which the control transfer instruction lies and appears directly in the instruction as an immediate displacement value. In this addressing mode, the displacement is computed relative to the content of the instruction pointer IP.

The Physical address to which the control will be transferred is given by the sum of 8 or 16 bit displacement and current content of IP. In case of jump instruction, if the signed displacement (d) is of 8 bits (i.e. –128<d<+128), we term it as short jump and if it is of

16     its (i.e. –32768<+32768), it is termed as long jump.

10    Intra-segment Indirect Mode:

 In this mode, the displacement to which the control is to be transferred, is in the same segment in which the control transfer instruction lies, but it is passed to the instruction indirectly. Here, the branch address is found as the content of a register or a memory location. This addressing mode may be used in unconditional branch instructions.

11. Inter-segment Direct Mode:

In this mode, the address to which the control is to be transferred is in a different segment. This addressing mode provides a means of branching from one code segment to another code segment. Here, the CS and IP of the destination address are specified directly in the instruction.

12.Inter-segment Indirect Mode:

In this mode, the address to which the control is to be transferred lies in a different segment and it is passed to the instruction indirectly, i.e. contents of a memory block containing four bytes, i.e. IP (LSB), IP (MSB), CS (LSB) and CS (MSB) sequentially. The starting address of the memory block may be referred using any of the addressing modes, except immediate mode.

Courtesy : internet sources