Transcript Base-plus-index addressing

Microprocessors
Chapter 3
Addressing Modes
prepared by
Dr. Mohamed A. Shohla
Chapter Overview
•
•
•
•
•
•
•
‫جام ع ة ال م نوف ي ة‬
Register Addressing
Immediate Addressing
Direct Data Addressing
Register Indirect Addressing
Base-Plus-lndex Addressing
Register Relative Addressing
Base Relative-Plus-lndex Addressing
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Data-Addressing Modes
•
Register addressing
•
Transfers a copy of a byte or word from the source register or memory location to
the destination register or memory location.
•
Immediate
addressing
Direct addressing
•
•
Register indirect
addressing
•
Transfers the source-immediate byte or word of data into the destination register
or memory location.
Moves a byte or word between a memory location and a register. The instruction
set does not support a memory-to-memory transfer, except for the MOVS
instruction.
Transfers a byte or word between a register and a memory location addressed by
an index or base register. The index and base registers are BP, BX, DI, and SI.
•
Base-plus-index
addressing
•
Transfers a byte or word between a register and the memory location addressed by
a base register (BP or BX) plus an index register (DI or SI).
•
Register relative
addressing
•
Moves a byte or word between a register and the memory location addressed by
an index or base register plus a displacement.
•
Base relative-plusindex addressing
•
Transfers a byte or word between a register and the memory location addressed by
a base and an index register plus a displacement.
•
Scaled-index
addressing
•
Is available only in the 80386 through the Pentium 4 microprocessor. The second
register of a pair of registers is modified by the scale factor of 2X, 4X, or 8X to
generate the operand memory address.
•
‫جام ع ة ال م نوف ي ة‬
•
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The MOV instruction
MOV
AX , BX
Destination
‫جام ع ة ال م نوف ي ة‬
Source
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Register Addressing
• Register addressing is the most common form of data addressing
and, once the register names are learned, is the easiest to apply.
•
Examples of the register-addressed instructions.
Assembly Language
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
‫جام ع ة ال م نوف ي ة‬
AL, BL
CH, CL
AX, CX
SP, BP
BX, ES
ECX, EBX
ESP, EDX
ES, DS
BL, DX
Size
8-bits
8-bits
16-bits
16-bits
16-bits
32-bits
32-bits
—
—
Operation
Copies BL into AL
Copies CL into CH
Copies CX into AX
Copies BP into SP
Copies ES into BX
Copies EBX into ECX
Copies EDX into ESP
Not allowed (segment-to-segment)
Not allowed (mixed sizes)
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Register Addressing Example :
MOV
BX, CX
The effect of executing the MOV BX, CX instruction at the
point just before the BX register changes. Note that only
the rightmost 16 bits of register EBX change.
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Immediate Addressing
• The term immediate implies that the data immediately follow the
hexadecimal opcode in the memory. Also note that immediate data
are constant data, while the data transferred from a register are
variable data.
•
Examples of the immediate-addressed instructions.
A s s e m b ly L a n g u a g e
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
‫جام ع ة ال م نوف ي ة‬
BL, 44
AX, 44H
CH, 100
A L , 'A '
A X , 'A B '
CL, 11001110B
EBX, 12340000H
E S I, 1 2
EAX, 100B
S ize
8 -b its
1 6 -b its
8 -b its
8 -b its
1 6 -b its
8 -b its
3 2 -b its
3 2 -b its
3 2 -b its
O p e ra tio n
C o p ie s
C o p ie s
C o p ie s
C o p ie s
C o p ie s
C o p ie s
C o p ie s
C o p ie s
C o p ie s
a 4 4 d e cim a l (2 C H ) in to B L
a 0 0 4 4 H in to A X
a 1 0 0 d e cim a l (6 4 H ) in to C H
a n A S C II A in to A L
a n A S C II B A in to A X
a 1 1 0 0 1 1 1 0 b in a ry in to C L
a 1 2 3 4 0 0 0 0 H in to E B X
a 1 2 d e cim a l in to E S I
a 1 0 0 b in a ry in to E A X
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Immediate Addressing Example:
MOV
EAX, 13456H
The operation of the MOV EAX,13456H instruction. This
instruction copies the immediate data (13456H) into EAX.
‫جام ع ة ال م نوف ي ة‬
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Direct Data Addressing
•
Direct addressing with a MOV instruction transfers data
between a memory location, located within the data segment,
and the AL (8-bit), AX (16-bit), or EAX (32-bit) register.
•
Examples of the Direct addressed instructions.
Assembly Language
‫جام ع ة ال م نوف ي ة‬
Size
MOV CH, DOG
8-bits
MOV CH, [1000H]
8-bits
MOV ES, DATA6
16-bits
MOV DATA7, BP
16-bits
MOV NUMBER, SP
16-bits
MOVDATA1, EAX
32-bits
MOV EDI, SUM1
32-bits
Operation
Copies the byte contents of data segment
memory location DOG into CH
Copies the byte contents of data segment
offset address 1000HintoCH
Copies the word contents of data
segment memory location DATA6 into ES
Copies BP into data segment memory
location DATA7
Copies SP into data segment memory
location NUMBER
Copies EAX into data segment memory
location DATA1
Copies the doubleword contents of data
segment memory location SUM1 into EDI
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Direct Addressing Example :
MOV AL, [1234H]
The operation of the MOV AL,[1234H] when DS = 1000H.
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Example
DATA1
DATA2
DATA3
DATA4
‫جام ع ة ال م نوف ي ة‬
.MODEL SMALL
.DATA
DB
10H
DB
0
DW
0
DW
0AAAAH
; select SMALL model
; indicate start of DATA segment
; place 10H in DATA1
; place 0 in DATA2
; place 0 in DATA3
; place AAAAH in DATA4
.CODE
.STARTUP
MOV
AL, DATA1
MOV
AH, DATA2
MOV
DATA3, AX
MOV
BX, DATA4
; indicate start of CODE segment
; indicate start of program
; copy DATA1 to AL
; copy DATA2 to AH
; save AX at DATA3
; load BX with DATA4
.EXIT
END
; exit to DOS
; end file
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Register Indirect Addressing
•
•
‫جام ع ة ال م نوف ي ة‬
Register indirect addressing allows data to be addressed at
any memory location through an offset address held in any of
the following registers: BP, BX, DI, and SI.
Examples of the Register indirect addressed instructions.
Assembly
Language
MOV CX, [BX]
Size
Operation
16-bits
MOV [BP], DL
8-bits
MOV [DI], BH
8-bits
MOV [DI], [BX]
—
MOV AL, [EDX]
8-bits
MOV ECX, [EBX]
32-bits
Copies the word contents of the data segment
memory location address by BX into CX
Copies DL into the stack segment memory
location addressed by BP
Copies BH into the data segment memory
location addressed by Dl
Memory-to-memory moves are not allowed
except with string instructions
Copies the byte contents of the data segment
memory location addressed by EDX into AL
Copies the doubleword contents of the data
segment memory location addressed by EBX
into ECX
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Register indirect Addressing Example :
MOV AX, [BX]
The operation of the MOV AX,[BX] instruction when BX = 1000H
and DS = 0100H. Note that this instruction is shown after the
contents of memory are transferred to AX.
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Base-Plus-lndex Addressing
•
Base-plus-index addressing is similar to indirect addressing
because it indirectly addresses memory data.
In the 8086 through the 80286, this type of addressing uses one
base register (BP or BX), and one index register (DI or SI) to
indirectly address memory.
•
•
Examples of the Base-Plus-Index addressed instructions.
A s s e m b ly L a n g u a g e
‫جام ع ة ال م نوف ي ة‬
S iz e
M O V C X ,[B X + D I]
1 6 -b its
M O V C H ,[B P + S I]
8 -b its
M O V [B X + S I],S P
1 6 -b its
M O V [B P + D I],A H
8 -b its
O p e ra tio n
C o p ie s th e w o rd c o n te n ts o f th e d a ta
s e g m e n t m e m o ry lo c a tio n a d d re s s b y B X
p lu s D l in to C X
C o p ie s th e b yte c o n te n ts o f th e s ta c k
s e g m e n t m e m o ry lo c a tio n a d d re s s e d b y B P
p lu s S I in to C H
C o p ie s S P in to th e d a ta s e g m e n t m e m o ry
lo c a tio n a d d re s s e s b y B X p lu s S I
C o p ie s A H in to th e s ta c k s e g m e n t m e m o ry
lo c a tio n a d d re s s e d b y B P p lu s D l
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Base-Plus-lndex Addressing Example :
MOV DX, [BX + DI]
An example showing how the base-plus-index addressing mode
functions for the MOV DX,[BX+DI] instruction. Notice that
memory address 02010H is accessed because DS = 0100H, BX
= 100H, and DI = 0010H.
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Example
.MODEL SMALL
.DATA
ARRAY DB 16 DUP (?)
DB 29H
DB 30 DUP (?)
.CODE
.STARTUP
MOV BX, OFFSET ARRAY
MOV DI, 10H
MOV AL, [BX+DI]
MOV DI, 20H
MOV [BX+DI], AL
.EXIT
END
‫جام ع ة ال م نوف ي ة‬
; select SMALL model
; start of DATA segment
; setup ARRAY
; sample data at element 10H
; start of CODE segment
; start of program
; address ARRAY
; address element 10H
; get element 10H
; address element 20H
; save in element 20H
; exit to DOS
; end of file
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Register Relative Addressing
•
•
Register relative addressing is similar to base-plus-index addressing and
displacement addressing. In register relative addressing, the data in a
segment of memory are addressed by adding the displacement to the
contents of a base or an index register (BP, BX, Dl, or SI).
Examples of the register Relative addressed instructions.
A s s e m b ly L a n g u a g e
S iz e
O p e ra tio n
M O V A X , [D I+ 1 0 0 H ]
1 6 -b its
M O V A R R A Y [S I], B L
8 -b its
M O V L IS T [S I+ 2 ], C L
8 -b its
M O V D I,S E T _ IT [B X ]
1 6 -b its
M O V A R R A Y [E B X ],E A X
3 2 -b its
C o p ie s th e w o rd c o n te n ts o f th e d a ta s e g m e n t
m e m o ry lo c a tio n a d d re s s e d b y D l p lu s 1 0 0 H
in to A X
C o p ie s B L in to th e d a ta s e g m e n t m e m o ry
lo c a tio n a d d re s s e d b y A R R A Y p lu s S I
C o p ie s C L in to th e d a ta s e g m e n t m e m o ry
lo c a tio n a d d re s s e d b y s u m o f L IS T , S I, a n d 2
C o p ie s th e w o rd c o n te n ts o f th e d a ta s e g m e n t
m e m o ry lo c a tio n a d d re s s e d b y th e s u m o f
S E T _ IT a n d B X in to D l
M o v e s E A X in to th e d a ta s e g m e n t m e m o ry
lo c a tio n a d d re s s e d b y th e s u m o f A R R A Y a n d
EBX
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Register Relative Addressing
MOV AX, [BX + 1000H]
The operation of the MOV AX,[BX+1000H] instruction,
when BX = 0100H and DS = 0200H.
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Register relative addressing used to
address an element of ARRAY.
The displacement addresses the start of ARRAY, and Dl accesses
an element.
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Example
.MODEL SMALL
.DATA
ARRAY DB 16 DUP (?)
DB 29H
DB 30 DUP (?)
.CODE
.STARTUP
MOV
DI, 10H
MOV
AL, ARRAY[DI]
MOV
DI, 20H
MOV
ARRAY[DI], AL
.EXIT
END
‫جام ع ة ال م نوف ي ة‬
; select SMALL model
; start of DATA segment
; setup ARRAY 00 ]
; sample data at element 10H
; start of CODE segment
; start of program
; address element 10H
; get element 10H
; address element 20H
; save in element 20H
; exit to DOS
; end of file
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Base Relative-Plus-lndex Addressing
Assembly Language
Size
Operation
MOV DH, [BX+DI+20H]
8-bits
Copies the byte contents of the data
segment memory location addressed by
the sum of BX, Dl, and 20H into DH.
MOV AX, FILE[BX+DI]
16-bits
Copies the word contents of the data
segment memory location addressed by
the sum of FILE, BX, and Dl into AX.
MOV LIST[BP+DI], CL
8-bits
Copies CL into the stack segment memory
location addressed by the sum of LIST,
BP, and Dl
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Base Relative-Plus-lndex Addressing
MOV AX, [BX+SI+100H]
• An example of base relative-plus-index addressing
using a MOV AX, [BX+SI+100H] instruction.
• Note: DS = 1000H.
‫جام ع ة ال م نوف ي ة‬
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Chapter 3
Questions and Answers
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What do the following MOV instructions
accomplish?
(a) MOV AX, BX
(b) MOV BX, AX
(c) MOV BL, CH
(d) MOV ESP, EBP
(e) MOV AX, CS
Instruction
Accomplish
(a) MOV AX, BX
Copy the contents of register BX into register AX
(b) MOV BX, AX
Copy the contents of register AX into register BX
(c) MOVBL, CH
Copy the contents of register CH into register BL
(d) MOV ESP, EBP
Copy the contents of register EBP into register ESP
(e) MOV AX, CS
Copy the contents of register CS into register AX
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List the 8-bit , 16-bit, and 32-bit registers
that are used for register addressing.
Registers
‫جام ع ة ال م نوف ي ة‬
8-bit
AH, AL, BH, BL, CH, CL, DH, DL
16-bit
AX, BX,CX, DX, SP, BP, DI, SI
32-bit
EAX, EBX,ECX, EDX, ESP, EBP, EDI, ESI
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Select an instruction for each of the following
tasks:
(a) copy EBX into EDX
(b) copy BL into CL
(c) copy SI into BX
(d) copy DS into AX
(e) copy AL into AH
Task
Instruction
(a) copy EBX into EDX
MOV EDX, EBX
(b) copy BL into CL
MOV CL, BL
(c) copy SI into BX
MOV BX, SI
(d) copy DS into AX
MOV AX, DS
(e) copy AL into AH
MOV AH, AL
‫جام ع ة ال م نوف ي ة‬
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Select an instruction for each of the following tasks:
(a) move a 12H into AL (b) move a 123AH into AX
(c) move a CDH into CL (d) move a 1000H into SI
(e) move a 1200A2H into EBX
Task
Instruction
(a) move a 12H into AL
MOV AL, 12H
(b) move a 123AH into AX
MOV AX, 123H
(c) move a CDH into CL
MOV CL, CDH
(d) move a 1000H into SI
MOV SI, 1000H
(e) move a 1200A2H into EBX
MOV EBX, 1200A2H
‫جام ع ة ال م نوف ي ة‬
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Suppose that DS = 0200H, BX= 0300H, and DI = 400H.
Determine the memory address accessed by each of the
following instructions, assuming real mode operation:
(a) MOV
AL, [1234H] (b) MOV
EAX, [BX]
(c) MOV
[DI], AL
(a) Starting address of the segment (DS)
2000H
+ displacement (1234H)
+ 1234H
Memory location address
(b) Starting address of the segment (DS)
+ displacement (BX)
+
Memory location address
(c) Starting address of the segment (DS)
+ displacement (DI)
+
Memory location address
‫جام ع ة ال م نوف ي ة‬
3234H
2000H
0300H
2300H
2000H
0400H
2400H
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Choose an instruction that requires BYTE
PTR, WORD PTR, DWORD PTR.
BYTE PTR
MOV BYTE PTR [DI], 33
WORD PTR
MOV WORD PTR [DI], 33
DWORD PTR
MOV DWORD PTR [DI], 33
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Suppose that DS = 1000H, SS = 2000H, BP = 1000H, and DI =
0100H. Determine the memory address accessed by each of
the following instructions, assuming real mode operation:
(a) MOV
AL, [BP+DI]
(b) MOV
CX, [DI]
(c) MOV
EDX, [BP]
(a) Starting address of the segment (SS)
+ Base (BP)
+ Index (DI)
Memory location address
20000H
+ 1000H
+ 0100H
21100H
(b) Starting address of the segment (DS)
+ displacement (DI)
10000H
+ 0100H
Memory location address
(c) Starting address of the segment (SS)
+ Base (BP)
Memory location address
‫جام ع ة ال م نوف ي ة‬
10100H
20000H
+ 1000H
21000H
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Suppose that DS = 1200H, BX = 0100H, and SI = 0250H.
Determine the address accessed by each of the following
instructions, assuming real mode operation:
(a) MOV
[100H], DL
(b) MOV
[SI+100H], EAX
(c) MOV
DL, [BX+100H]
(a) Starting address of the segment (DS)
+ displacement (100H)
Memory location address
12000H
+ 100H
12100H
(b) Starting address of the segment (DS)
+ register SI (0250H)
+ displacement (100H)
Memory location address
12000H
+ 0250H
+
100H
12350H
(c) Starting address of the segment (SS)
+ register BX (0100H)
+ displacement (100H)
Memory location address
20000H
+ 0100H
+ 0100H
20200H
‫جام ع ة ال م نوف ي ة‬
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Suppose that DS = 1100H, BX = 0200H, LIST = 0250H, and SI =
0500H, determine the address accessed by each of the
following instructions, assuming real mode operation:
(a) MOV
LIST[SI], EDX (b) MOV
CL, LIST[BX+SI]
(c) MOV
CH, [BX+SI]
(a) Starting address of the segment (DS)
+ address of List (0250H)
+ register SI (0500H)
Memory location address
(b) Starting address of the segment (DS)
+ address of List (0250H)
+ register BX (0200H)
+ register SI (0500H)
Memory location address
(c) Starting address of the segment (DS)
+ register BX (0200H)
+ register SI (0500H)
Memory location address
‫جام ع ة ال م نوف ي ة‬
+
+
11000H
0250H
0500H
11750H
+
+
+
11000H
0250H
0200H
0500H
11950H
+
+
11000H
0200H
0500H
11700H
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Suppose that DS = 1300H, SS = 1400H, BP = 1500H, and SI =
0100H. Determine the address accessed by each of the
following instructions, assuming real mode operation:
(a) MOV
EAX, [BP+200H]
(b) MOV
AL, [BP+SI-200H]
‫جام ع ة ال م نوف ي ة‬
(a) Starting address of the segment (SS)
+ register BP (1500H)
+ displacement (200H)
Memory location address
14000H
+ 1500H
+
200H
15700H
(b) Starting address of the segment (SS)
+ register BP (1500H)
+ register SI (0100H)
- displacement (200H)
Memory location address
14000H
+ 1500H
+ 0100H
200H
15400H
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Suppose that DS = 1300H, SS = 1400H, BP = 1500H, and SI =
0100H. Determine the address accessed by each of the
following instructions, assuming real mode operation:
(a) MOV
EAX, [BP+200H]
(b) MOV
AL, [BP+SI-200H]
‫جام ع ة ال م نوف ي ة‬
(a) Starting address of the segment (SS)
+ register BP (1500H)
+ displacement (200H)
Memory location address
14000H
+ 1500H
+
200H
15700H
(b) Starting address of the segment (SS)
+ register BP (1500H)
+ register SI (0100H)
- displacement (200H)
Memory location address
14000H
+ 1500H
+ 0100H
200H
15400H
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