![Continuation……….
In X(Ri)
X denotes the constant value contained in the instruction
and
Ri is the name of the register involved.
The effective address of the operand is given by
EA = X+[Ri].
The contents of the index registers are not changed in the
process of generating the effective address.
The value X defines an offset also called as a
displacement.](https://image.slidesharecdn.com/addressingmodes-150331205849-conversion-gate01/85/Addressing-modes-10-320.jpg)
![C-Language for bubble sorting
for (j=n-1;j>0;j=j-1)
{
for(k=j-1;k>0;k=k-1)
{
if(List[k]>List[j])
{
Temp=List[k];
List[k]=List[j];
List[j]=Temp;
}
}
}](https://image.slidesharecdn.com/addressingmodes-150331205849-conversion-gate01/85/Addressing-modes-22-320.jpg)
Addressing modes
- 2. ADDRESSING MODES By Nithin Santhosh
- 3. WHAT IS ADDRESSING MODE? The different ways in which location of an operand is specified in an instruction are referred to as “Addressing Modes”. The different types of generic addressing modes are Immediate, Register, Absolute(Direct), Indirect, Index, Base with index, Base with index and offset, Relative, Autoincrement, Autodecrement .
- 4. Register Addressing Mode Register addressing mode involves the use of registers to hold the data to be manipulated. Eg : Mov A,R0 Mov R1,R0 Mov Res,R1 In this mode operand is the content of a processor register.
- 5. ABSOLUTE MODE(DIRECT MODE) In the absolute or direct addressing mode, the data is in a ram memory location whose address is known, and this address is given as a part of the instruction. Eg : Mov Loc,R1
- 6. IMMEDIATE ADDRESSING MODE In this addressing mode, the source operand is a constant. In immediate addressing mode, as the name indicates when the instruction is assembled, the operand comes immediately after the opcode. In this addressing mode the data must be immediately preceded by the pound sign, ‘#’;
- 7. INDIRECT ADDRESSING MODE In this addressing mode, the instruction does not give the operand or its address explicitly. This addressing mode provides information from which the memory address or the operand can be determined. This address is the effective address of the operand. When we use this addressing mode here actually the register acts as a pointer, where pointer is nothing but the register or memory location that contains the address of an operand.
- 8. Continuation….. Example : Move N,R1 Move #Num1,R2 Clear R0 LOOP: Add (R2),R0 Add #4,R2 Decrement R1 Branch>0 LOOP Move R0,Sum
- 9. INDEX ADDRESSING MODE This is useful in dealing with lists and arrays. The effective address of the operand is generated by adding a constant value to the contents of the register. The register used may be either a special function register or general purpose register, the register which we use here is known as “index register”. We indicate the Index mode symbolically as X(Ri).
- 10. Continuation………. In X(Ri) X denotes the constant value contained in the instruction and Ri is the name of the register involved. The effective address of the operand is given by EA = X+[Ri]. The contents of the index registers are not changed in the process of generating the effective address. The value X defines an offset also called as a displacement.
- 11. Continuation……. Move #LIST,R0 Clear R1 Clear R2 Clear R3 Move N,R4 Add 4(R0),R1 Add 8(R0),R2 Add 12(R0),R3 Add #16,R0 Decrement R4 Branch>0 LOOP Move R1,SUM1 Move R2,SUM2 Move R3,SUM3 LOOP:
- 12. RELATIVE ADDRESSING MODE In this addressing mode the effective address is determined by the Index mode using the program counter in the place of general purpose register Ri.
- 13. ADDITIONAL MODES The two additional modes are Autoincrement and Autodecrement mode. Autoincrementmode – The effective address of the operand is the contents of a register specified in the instruction. After accessing the operand, the contents of this register are automatically incremented to point to the next item in a list. The autoincrement mode is written as (Ri)+ Autodecrementmode - The contents of a register specified in the instruction are first automatically decremented and are then used as the effective address of the operand. The Autodecrementmode is written as -(Ri)
- 14. ADVANTAGE OF INDIRECT OVERDIRECT MODE In direct addressing mode we cannot use loops, and in case of indirect addressing mode we can use loop.
- 15. QUESTIONS Registers R1 and R2 of a computer contain the decimal values 1200 and 4600. What is the effective address of the memory operand in each of the following instructions? Q1. i) Load 20(R1),R5 a) 20 b) 4600 c)1220 d)1200 Ans : 1220
- 16. ii) Move #3000,R5 a)1220 b)1400 c)4600 d)None of the above Ans : d) None of the above iii) Store R5,30(R1,R2) a)5830 b)5600 c)1200 d)4600 Ans : a)5830
- 17. iv) Add -(R2),R5 v) Add (R1)+,R5 a)1200 b)4599 c)1199 d)4600 Ans : b)4599 a)1199 b)1200 c)1198d)1201 Ans : d)1199
- 18. Q 2. Identify the addressing modes i) ADD #6,R1 a)Register b)Absolute(Direct) c)Indirect d)Index e)Immediate Ans : a) and e) ii) ADD R1 a)Register b)Absolute(Direct) c)Indirect d)Index e)Immediate Ans : a)
- 19. iii) ADD (R1)+,R5 a)Increment Mode b)Absolute(Direct) c) Autoincrement Mode d)Index e)Immediate Ans : C) Autoincrement Mode iv) Load 20(R1),R5 a)Base with index and offset b)Absolute(Direct) c)Indirect d)Index e)Immediate Ans : d)Index
- 20. v) Store R5,30(R1,R2) a)Base with index and offset b)Absolute(Direct) c)Indirect d)Index e)Immediate Ans : a)Base with index and offset
- 21. Sorting The process of rearranging the elements so that they are in ascending or descending order is called as sorting The various types of sorting are bubble sort, quick sort, insertion sort etc…
- 22. C-Language for bubble sorting for (j=n-1;j>0;j=j-1) { for(k=j-1;k>0;k=k-1) { if(List[k]>List[j]) { Temp=List[k]; List[k]=List[j]; List[j]=Temp; } } }
- 23. ALP For Bubble Sorting Move #LIST,R0 Move N,R1 Subtract #1,R1 OUTER Move R2,R2 Subtract #1,R1 MoveByte (R0,R1),R3 INNER CompareByte R3,(R0,R2) Branch<=0 NEXT MoveByte (R0,R2),R4 MoveByte R3,(R0,R2) MoveByte R4,(R0,R1) MoveByte R4,R3 NEXT Decrement R2 Branch>=0 INNER Decrement R1 Branch>0 OUTER
- 24. END!!!!!