microprocessor pdf - م.م.أنمار خليل

ﺤﺎﺴﺒﺎﺕ ﻤﺘﻘﺩﻤﺔ ﺍﻟﻤﺭﺤﻠﺔ ﺍﻟﺜﺎﻟﺜﺔ ﻫﻨﺩﺴﺔ ﻜﻬﺭﻭ ﻤﻴﻜﺎﻨﻴﻙ ﺍﻟﻤﺩﺭﺱ ﻤﺴﺎﻋﺩ ﺍﻨﻤﺎﺭ ﺨﻠﻴل ﺍﺒﺭﺍﻫﻴﻡ

١٤

Instruction Set of 8086 Processor

1- Data transfer Group

1. MOV Instruction

Flags affected

Operation

Format

meaning

Mnemonic

None

(S) (D)

MOV D,S

move

MOV

ﻭﻫﻭ ﺍﻴﻌﺎﺯ ﻴﻘﻭﻡ

ﺒﺎﺩﺨﺎل ﻋﺩﺩ ﻤﺒﺎﺸﺭ ﻤﻥ ﻗﺒل ﺍﻟﻤﺴﺘﺨﺩﻡ

ﺍﻭ ﻨﻘل

)

ﻤﺤﺘﻭﻯ ﻤﺴﺠل

ﺍﻭ

ﻤﺤﺘﻭﻯ ﺫﺍﻜﺭﺓ

(

ﺍﻟﻰ

ﻤﺤﺘﻭﻯ

ﻤﺴﺠل ﺍﺨﺭ

ﺍﻭ

ﻤﻭﻗﻊ ﺫﺍﻜﺭﺓ ﺍﺨﺭ

ﻤﻼﺤﻅﺔ

ﻋﻨﺩ ﺍﻟﺘﻌﺎﻤل ﻤﻊ ﺍﻟﺫﺍﻜﺭﺓ ﺒﺸﻜل ﻤﺒﺎﺸﺭ

)

ﻋﻨﻭﺍﻥ ﻤﺒﺎﺸﺭ

(

ﻴﺠﺏ ﺍﺘﺒﺎﻉ ﺍﻟﺨﻁﻭﺍﺕ ﺍﻟﺘﺎﻟﻴﺔ

ﻓﻲ ﺠﺯﺀ ﻤﻘﻁﻊ ﺍﻟﺒﻴﺎﻨﺎﺕ

.DATA
D1 DW 9A23H
D2 DB 22H

ﺤﻴﺙ ﺘﻤﺜل ﻜل ﻤﻥ

ﻭ

ﻋﻨﻭﺍﻨﻴﻥ ﻤﺒﺎﺸﺭﺓ ﺍﻭ ﺍﺯﺍﺤﺎﺕ ﻤﺒﺎﺸﺭﺓ ﻀﻤﻥ ﻤﻘﻁﻊ ﺍﻟﺒﻴﺎﻨﺎﺕ ﻭﻜﺎﻻﺘﻲ

ﺘﻌﺭﻑ

ﺒﻴﺎﻨﺎﺕ ﺒﻁﻭل ﻜﻠﻤﺔ ﻭﺒﻘﻴﻤﺔ

9A23H

ﻤﺨﺯﻭﻨﺔ ﻓﻲ ﺍﺯﺍﺤﺔ ﻤﻌﻁﺎﺓ ﻤﻥ ﻗﺒل ﺍﻟﻤﻌﺎﻟﺞ ﻀﻤﻥ ﻤﻘﻁﻊ ﺍﻟﺒﻴﺎﻨﺎﺕ ﻭﻤﻌﺭﻓﺔ

ﻟﻠﻤﺴﺘﺨﺩﻡ ﺒﺎﻟﺭﻤﺯ

ﺒﻴﻨﻤﺎ

ﺒﻴﺎﻨﺎﺕ ﺒﻁﻭل ﺒﺎﻴﺕ ﻭﺒﻘﻴﻤﺔ

22H

ﻤﺨﺯﻭﻨﺔ ﻓﻲ ﺍﺯﺍﺤﺔ ﻤﻌﻁﺎﺓ ﻤﻥ ﻗﺒل ﺍﻟﻤﻌﺎﻟﺞ ﻀﻤﻥ ﻤﻘﻁﻊ ﺍﻟﺒﻴﺎﻨﺎﺕ ﻭﻤﻌﺭﻓﺔ

ﻟﻠﻤﺴﺘﺨﺩﻡ ﺒﺎﻟﺭﻤﺯ

ﻭﻴﺘﻡ ﺍﺴﺘﺨﺩﺍﻤﻬﺎ ﺒﺎﻟﺒﺭﻨ

ﺎﻤﺞ ﺒﺎﻟﺸﻜل ﺍﻟﺘﺎﻟﻲ

MOV SI,D1
MOV CL,D2

ﻭﺒﻌﺩ ﺍﻟﺘﻨﻔﻴﺫ ﻓﺎﻥ ﻗﻴﻡ ﺍﻟﻤﺴﺠﻼﺕ ﺴﺘﻜﻭﻥ

SI=9A23H
CX=0022H

ﻭﻴﺠﺏ ﺍﻥ ﻨﺭﺍﻋﻲ ﺍﻥ ﻴﺜﺒﺕ ﺒﻌﺩ ﻜﺘﺎﺒﺔ ﺍﻟﺭﻗﻡ ﻓﻲ ﻤﻘﻁﻊ ﺍﻟﺒﻴﺎﻨﺎﺕ ﺤﺭﻑ

ﻭﺍﻟﺫﻱ ﻴﻤﺜل ﺭﻤﺯ ﺍﻟﻨﻅﺎﻡ ﺍﻟﺴﺎﺩﺱ ﻋﺸﺭﻱ

ﻋﻨﺩ ﺍﺩﺨﺎل ﺍﺭﻗﺎﻡ ﻤﺒﺎﺸﺭﺓ ﺍﻟﻰ ﻤﺴﺠل ﻴﺠﺏ ﺍﻥ ﻨﺭﺍﻋﻲ ﺍﻥ ﻜﺎﻥ ﺍﻟﺭﻗﻡ ﻴﺒﺩ

ﺃ ﺒﺤﺭﻑ ﻤﻥ ﺍﻟﺤﺭﻭﻑ ﺍﻟﺘﻲ ﺘﻤﺜل ﺍﻻﺭﻗﺎﻡ ﻤﻥ

ﺍﻟﻰ

ﺍﻱ

)

A,B,C,D,E,F

(

ﻴﺠﺏ ﺍﻥ ﻴﻀﺎﻑ

ﻗﺒل ﺍﻟﺭﻗﻡ ﺤﺘﻰ ﻻﻴﻔﺴﺭ ﻤﻨﻘﺒل ﺍﻟﻤﻌﺎﻟﺞ ﻋﻠﻰ ﺍﻨﻪ ﺤﺭﻭﻑ ﻭﻟﻴﺱ ﺭﻗﻡ ﻓﻤﺜﻼ

ﻋﻨﺩ ﺍﺩﺨﺎل ﺍﻟﺭﻗﻡ

AB23

ﺍﻟﻰ ﺍﻟﻤﺴﺠل

ﻴﺠﺏ ﺍﻥ ﻴﻜﺘﺏ ﺍﻻﻴﻌﺎﺯ ﻜﺎﻟﺘﺎﻟﻲ

MOV CX,0AB23

٢٤

ﻋﻨﺩ ﺍﺩﺨﺎل ﺭﻗﻡ ﻤﺒﺎﺸﺭ ﺍﻟﻰ ﻋﻨﻭﺍﻥ ﺍ

ﻭ ﺍﺯﺍﺤﺔ ﻤﻌﻨﻭﻨﺔ ﺒﺸﻜل ﻤﺒﺎﺸﺭ ﻓﻲ ﻤﻘﻁﻊ ﺍﻟﺒﻴﺎﻨﺎﺕ ﻓﻴﺘﻡ ﺘﻌﺭﻴﻑ ﺍﻟﻌﻨﻭﺍﻥ ﺍﻟﻤﺒﺎﺸﺭ

ﺒﺎﻟﺸﻜل ﺍﻟﺘﺎﻟﻲ

.DATA
D3 DB ?
D4 DW ?

ﻭﻴﺘﻡ ﺍﺩﺨﺎل ﺍﻟﺒﻴﺎﻨﺎﺕ ﻀﻤﻥ ﻤﻘﻁﻊ

CODE

ﺒﺎﻟﺸﻜل ﺍﻟﺘﺎﻟﻲ

MOV D3,0AFH
MOV D4,98CEH

ﻻﻴﻤﻜﻥ ﻨﻘل ﺍﻟﺒﻴﺎﻨﺎﺕ ﺒﺸﻜل ﻤﺒﺎﺸﺭ ﻤﻥ ﻤﻭﻗﻊ ﺫﺍﻜﺭﺓ ﺍﻟﻰ ﻤﻭﻗﻊ ﺫﺍﻜ

ﺭﺓ ﺍﺨﺭ ﻭﺍﻨﻤﺎ ﻴﺠﺏ ﺍﻥ ﻴﻜﻭﻥ ﺍﺤﺩ ﻤﺴﺠﻼﺕ ﺍﻟﻤﻌﺎﻟﺞ

ﻤﻨﻁﻘﺔ ﻭﺴﻁﻴﺔ ﻓﻤﺜﻼ

ﻟﻨﻘل ﺍﻟﻤﻭﻗﻊ

ﺍﻟﻰ

ﻭﺍﻟﺘﻲ ﺘﺤﺘﻭﻱ ﻋﻠﻰ ﺍﻟﻘﻴﻡ ﺍﻟﺘﺎﻟﻴﺔ

67H

ﻭ

ﻓﻴﻜﺘﺏ ﺍﻟﺒﺭﻨﺎﻤﺞ ﺒﺎﻟﺸﻜل ﺍﻟﺘﺎﻟﻲ

.DATA
D1 DB  67H
D2 DB  4BH
.CODE
MOV  AL,D1
MOV  D2,AL

1-1THE STACK : the stack is implemented in the memory of 8086, and it is used for

temporary storage.

Starting address of stack memory (top of the stack) obtained from the contents of the stack

pointer (SP) and the stack segment (SS) (SS:SP). Figure 1 shows the stack region for

SS=0400H and SP=A000H. Data transferred to and from the stack are word-wide, not byte-

wide. Whenever a word of data is pushed onto the top of the stack, the high-order 8 bits are

placed in the location addressed by SP-1. the low-order 8 bits are placed in the location

addressed by SP-2.The SP is then decremented by 2.

Whenever data are popped from the stack, the low-order 8-bits are removed from the location

addressed by SP. The high-order 8 bits are removed from the location addressed by SP+1. The

SP is then incremented by 2.

ﺍﻟﻤﻜﺩﺱ

ﻴﺘﻡ ﺘﻁﺒﻴﻕ ﺍﻟﻤﻜﺩﺱ

ﻓﻲ ﺫﺍﻜﺭﺓ ﺍﻟﻤﻌﺎﻟﺞ

٦٨٠٨

ﻭﺘﺴﺘﺨﺩﻡ ﻟﻠﺨﺯﻥ ﺍﻟﻭﻗﺘﻲ

٣٤

ﻴﺘﻡ ﺍﻟﺤﺼﻭل ﻋﻠﻰ ﻋﻨﻭﺍﻥ ﺍﻟﺒﺩﺍﻴﺔ ﻟﺫﺍﻜﺭﺓ ﺍﻟﻤﻜﺩﺱ

)

ﻗﻤﺔ ﺍﻟﻤﻜﺩﺱ

(

ﻭﺍﻟﺫﻱ ﻴﺘﻡ ﺍﻟﺤﺼﻭل ﻋﻠﻴﻪ ﻤﻥ ﺨﻼل ﻤﺤﺘﻭﻯ ﻤﺅﺸﺭ ﺍﻟﻤﻜﺩﺱ

ﻭﻤﺴﺠل ﻤﻘﻁﻊ ﺍﻟﻤﻜﺩﺱ

)

SS:SP

ﻭﺍﻟﺸﻜل ﺭﻗﻡ

ﻴﺒﻴﻥ ﻤﻨﻁﻘﺔ ﺍﻟﻤﻜﺩﺱ ﺒﻘﻴﻤﺔ

SS=0400H

ﻭ

SP=A000H

ﻭﺍﻟﺒﻴﺎﻨﺎﺕ ﺍﻟﺘﻲ ﺍﻟﺘﻲ ﻴﺘﻡ ﺘﻨﺎﻗﻠﻬﺎ ﻤﻥ ﻭﺍﻟﻰ ﺍﻟﻤﻜﺩﺱ ﻫﻲ ﻤﻥ ﻨﻭﻋﻴﺔ ﺍﻟﻜﻠﻤﺔ

word

ﻭﻟﻴﺴﺕ ﻤﻥ ﻨﻭﻋﻴﺔ ﺍﻟﺒﺎﻴﺕ

ﻭﻋﻨﺩﻤﺎ ﻴﺘﻡ ﺩﻓﻊ

push

ﻗﻴﻤﺔ ﻓﻲ ﻗﻤﺔ ﺍﻟﻤﻜﺩﺱ ﻓﺎﻥ

high order 8bit

ﺴﺘﻭﻀﻊ ﻓﻲ ﺍﻟﻤﻭﻗﻊ ﺍﻟﺫﻱ ﻋﻨﻭﺍﻨﻪ ﻫﻭ ﻗﻴﻤﺔ

ﻤﻁﺭﻭﺡ ﻤﻨﻪ ﻭﺍﺤﺩ

ﻊـﻀﻭﻴ ﺎﻤﻨﻴﺒ

Low order 8bit

ﻓﻲ ﺍﻟﻤﻭﻗ

ﻊ ﺍﻟﺫﻱ ﻋﻨﻭﺍﻨﻪ ﻫﻭ ﻗﻴﻤﺔ

ﻤﻁﺭﻭﺡ ﻤﻨﻪ ﺍﺜﻨﻴﻥ

ﻭﻴﺘﻡ

ﻁﺭﺡ ﺍﺜﻨﻴﻥ ﻤﻥ ﻗﻴﻤﺔ

ﻭﻋﻨﺩﻤﺎ ﻴﺘﻡ ﺍﺨﺭﺍﺝ ﺍﻟﺒﻴﺎﻨﺎﺕ ﻤﻥ ﺍﻟﻤﻜﺩﺱ ﻓﺎﻥ

low-order 8-bits

ﻴﺘﻡ ﺭﻓﻌﻬﺎ ﻤﻥ ﺍﻟﻤﻭﻗ

ﻊ ﺍﻟﻤﻌ

ﻨﻭﻥ ﺒﻘﻴﻤﺔ

ﺒﻴﻨ

ﻤﺎ

high-order 8-bits

ﻴﺘﻡ ﺭﻓﻌﻬﺎ ﻤﻥ ﺍﻟﻤﻭﻗﻊ ﺍﻟﻤﻌﻨﻭﻥ ﺒﻘﻴﻤﺔ

SP+1

ﻭﻗﻴﻤﺔ

ﻴﻀﺎﻑ ﻟﻪ ﺍﺜﻨﻴﻥ

Figure 1 The stack region

The following example illustrates pushing the content of the AX and BX registers onto the

stack and then subsequently popping the data from the stack back to the registers. Assume that

0400:FFFFH

0400:A000H

Stack segment

End of stack

Top of stack

Bottom of stack

٤٤

the AX contains hex 026B, the BX contains 04E3, and the SP contains 36 ( the segment address

in the SS does not concern us here)

ﻭﺍﻟﻤﺜﺎل ﺍﻟﺘﺎﻟﻲ ﻴﺒﻴﻥ ﻟﻨﺎ ﻜﻴﻔﻴﺔ ﺍﺩﺨﺎل ﻤﺤﺘﻭﻴﺎﺕ ﺍﻟﻤﺴﺠﻠﻴﻥ

AX and BX

ﻓﻲ ﺍﻟﻤﻜﺩﺱ ﻭﻤﻥ ﺜﻡ ﺒﺸﻜل ﺘﻌﺎﻗﺒﻲ ﺍﺨﺭﺍﺝ

ﺍﻟﻤﻌﻠﻭﻤﺎﺕ ﻤﻥ ﺍﻟﻤﻜﺩﺱ ﻭﺍﺭﺠﺎﻋﻬﺎ ﺍﻟﻰ ﻤﻜﺎﻨﻬﺎ ﺍﻻﻭل ﻓﻲ ﺍﻟﻤﺴﺠﻠﻴﻥ

ﻭﺒﺎﻓﺘﺭﺍﺽ ﺍﻥ ﺍﻟﻤﺴﺠل

ﻴﺤﻭﻱ ﺍﻟﺭﻗﻡ

026B

ﺒﻨﻅﺎﻡ ﺍﻟﺴﺎﺩﺱ ﺍﻟﻌﺸﺭﻱ ﻭﺍﻟﻤﺴﺠل

ﻴﺤﻭﻱ ﺍﻟﻘﻴﻤﺔ

04E3

ﻭﻤﺴﺠل

ﻴ

ﺤﻭﻱ ﺍﻟﻘﻴﻤﺔ

ﻭﻻﻨﻬﺘﻡ ﺒﻘﻴﻤﺔ

1. Initially, the stack is empty and looks like this

2. PUSH AX: Decrements the SP by 2 (to 34) and stores the contents of the AX,026B, in the

stack. Note that the operation reverses the sequence of the stored bytes, so that 026B becomes

6B02:

3. PUSH BX: Decrements the SP by 2 (to 32) and stores the contents of the BX,04E3, in the

stack as E304:

4. POP BX: Restores the word from where the SP points in the stack (E304) to the BX register

and increments the SP by 2 (to 34). The BX now contains 04E3, with the bytes correctly

restored. The stack now appears as:

....

Segment address of stack

SP=36

Top of stack

....

6B02

SP=34

....

E304

6B02

SP=32

٥٤

5. POP AX: Restores the word from where the SP points in the stack (6B02) to the AX register

and increments the SP by 2 (to 36). The BX now contains 026B, with the bytes correctly

restored. The stack now appears as:

Note that POP instructions are coded in reverse sequence from PUSH instructions; the example

pushed the AX and BX registers, but popped the BX and AX, in that order .Also, the values

pushed onto the stack are still there, although the SP no longer points to them.

ﻨﻼﺤﻅ ﺍﻥ ﺍﻴﻌﺎﺯﺍﺕ

POP

ﺘﻌﻤل ﺒﺸﻜل ﻤﻌﺎﻜﺱ ﻻﻴﻌﺎﺯﺍﺕ

PUSH

ﻓﻘﺩ ﻗﻤﻨﺎ ﺒﺎﺩﺨﺎل

ﺜﻡ

ﻭﻨﺨﺭﺝ

ﺜﻡ

ﻤﻊ

ﺍﻻﻟﺘﺯﺍﻡ ﺒﺎﻟﺘﺭﺘﻴﺏ ﻭﻜﺫﻟﻙ ﺍﻟﻘﻴﻡ ﺍﻟﺘﻲ ﺍﺩﺨﻠﺕ ﺍﻟﻰ ﺍﻟﻤﻜﺩﺱ ﺒﻘﻴﺕ ﻫﻨﺎﻙ ﻤﻊ ﺍﻥ

ﻟﻡ ﻴﻌﺩ ﻴﺅﺸﺭ ﻋﻠﻴﻬﺎ

1-2The MOV instruction : The function of MOV instruction is to transfer a byte or word of

data from a source location to a destination location. The general form of MOV instruction is as

shown below:

ﺍﻥ ﻭﻅﻴﻔﺔ ﺍﻴﻌﺎﺯ

MOV

ﻫﻭ ﻟﻨﻘل ﺒﺎﻴﺕ ﺍﻭ ﻜﻠﻤﺔ

ﻤﻥ ﺍﻟﺒﻴﺎﻨﺎﺕ ﻤﻥ ﻤﻭﻗﻊ ﺍﻟﻤﻨﻁﻠﻕ ﺍﻟﻰ ﻤﻭﻗﻊ ﺍﻟﻤﺴﺘﻘﺭ ﻭﺍﻟﺼﻴﻐﺔ ﺍﻟﻌﺎﻤﺔ ﻟﻼﻴﻌﺎﺯ

MOV

ﻫﻭ ﻜﺎﻻﺘﻲ

Flags affected

Operation

Format

meaning

Mnemonic

None

(S) (D)

MOV D,S

move

MOV

From table 1-(a) , we see that data can be moved between general purpose registers, between a

general purpose – register and a segment register, between a general purpose-register or

....

E304

6B02

SP=34

....

E304

6B02

SP=36

٦٤

segment register and memory, or between a memory location and the accumulator. Note that

memory-to-memory transfers are not allowed.

ﻭﻤﻥ ﺨﻼل ﺍﻟﺠﺩﻭل

1-(a)

ﻨﺭﻯ ﺍﻥ ﺍﻟﺒﻴﺎﻨﺎﺕ ﻴﻤﻜﻥ ﺍﻥ ﺘﻨﺘﻘل ﺒﻴﻥ ﻤﺴﺠﻼﺕ ﺍﻻﺴﺘﺨﺩﺍﻡ ﺍﻟﻌﺎﻡ ﺍﻭ ﺒﻴﻥ ﻤﺴﺠﻼﺕ ﺍﻻﺴﺘﺨﺩﺍﻡ ﺍﻟﻌﺎﻡ

ﻭﻤﺴﺠﻼﺕ ﺍﻟﻤﻘﺎﻁﻊ ﺍﻭﺒﻴﻥ ﻤﺴﺠﻼﺕ ﺍﻻﺴﺘﺨﺩﺍﻡ ﺍﻟﻌﺎﻡ ﺍﻭ ﻤﺴﺠﻼﺕ ﺍﻟﻤﻘﺎﻁﻊ ﻤﻊ ﺍﻟﺫﺍﻜﺭﺓ ﺍﻭ ﺒﻴﻥ ﻤﻭﺍﻗﻊ ﺍﻟﺫﺍﻜﺭﺓ ﻭﺍﻟﻤﺭﻜﻡ

ﻭﻻﺤﻅ ﺍﻨﻪ ﻻﻴﻭﺠﺩ ﺘﻨﺎﻗل ﻤﺒﺎﺸﺭ ﺒﻴﻥ ﻤﻭﺍﻗﻊ ﺍﻟﺫﺍﻜﺭﺓ

1-3PUSH / POP: The PUSH and POP instructions are important instructions that are store and

retrieve data from the LIFO (Last In First Out) stack memory. The general forms of PUSH and

POP instructions are as shown below:

ﺍﻥ ﺍﻴﻌﺎﺯﻱ

PUSH/POP

ﻫﻲ ﻤﻥ ﺍﻻﻴﻌﺎﺯﺍﺕ ﺍﻟﻤﻬﻤﺔ ﻭﺍﻟﺘﻲ ﺘﻘﻭﻡ ﺒﺨﺯﻥ ﻭﺍﺴﺘﻌﺎﺩﺓ ﺍﻟﻤﻌﻠﻭﻤﺎﺕ ﺫﺍﻜﺭﺓ ﺍﻟﻤﻜﺩﺱ

)

ﺍﺨﺭ ﻤﻥ ﻴﺩﺨل

ﺍﻭل ﻤﻥ ﻴﺨﺭﺝ

(

ﻭﺍﻟﺼﻴﻐﺔ ﺍﻟﻌﺎﻤﺔ ﻟﻼﻴﻌﺎﺯﻱ

PUSH

ﻭ

POP

ﻭﻜﻤﺎ ﻓﻲ ﺍﺩﻨﺎﻩ

Operand (S or D)

Flags

Operation

Format

Meaning

Mnemonic

Seg reg (CS illegal

Memory

Flag register

None

((SP)) (S)

(SP) (SP)-2

PUSH S

Push word onto

stack

PUSH

None

(D) ((SP))

(SP) (SP)+2

POP D

POP word onto

stack

POP

1-4 LEA, LDS, and LES(load – effective address) INSTRUCTIONS:

These instructions load a segment and general purpose registers with an address directly from

memory. The general forms of these instructions are as shown below:

ﻫﺫﻩ ﺍﻻﻴﻌﺎﺯﺍﺕ ﺘﺤﻤل ﻤﺴﺠل ﺍﻟﻤﻘﻁﻊ ﻭﻤﺴﺠﻼﺕ ﺍﻻﺴﺘﺨﺩﺍﻡ ﺍﻟﻌﺎﻡ ﺒﻌﻨﻭﺍﻥ ﻤﺒﺎﺸﺭ ﻤﻥ ﺍﻟﺫﺍﻜﺭﺓ

ﻭﺍﻟﺼﻴﻐﺔ ﺍﻟﻌﺎﻤ

ﺔ ﻟﻬﺫﻩ

ﺍﻻﻴﻌﺎﺯﺍﺕ ﻤﺒﻴﻨﺔ ﻓﻲ ﺍﺩﻨﺎﻩ

Flags affected

Operation

Format

meaning

Mnemonic

None

EA (reg16)

LEA reg16,EA

Load effective address

LEA

٧٤

None

[PA] (reg16)

[PA+2] (DS)

LDS reg16,EA

Load register and DS

LDS

None

[PA] (reg16)

[PA+2] (ES)

LES reg16,EA

Load register and ES

LES

The LEA instruction is used to load a specified register with a 16 – bit effective address(EA).

ﺍﻥ ﺍﻴﻌﺎﺯ

LEA

ﻫﻭ ﻴﺴﺘﺨﺩﻡ ﻟﺘﺤﻤﻴل ﻤﺴﺠل ﻤﻌﻴﻥ ﺒﻌﻨﻭﺍﻥ ﻓﻌﺎل ﺒﻁﻭل

16-bit

The LDS instruction is used to load a specified register with the contents of PA and PA+1

memory locations, and load DS with the contents of PA+2 and PA+3 memory locations.

ﺍﻥ ﺍﻴﻌﺎﺯ

LDS

ﻴ

ﺴﺘﺨﺩﻡ ﻓﻲ ﻋﻤﻠﻴﺔ ﺘﺤﻤﻴل ﻤﺴﺠل

ﻤﻌﻴﻥ

ﺒﻤﺤﺘﻭﻯ ﻤﻭﺍﻗﻊ ﺍﻟﺫﺍﻜﺭﺓ

ﻭ

PA+1

ﻭﺘﺤﻤﻴل

ﺒﻤﺤﺘﻭﻯ ﻤﻭﺍﻗﻊ

ﺍﻟﺫﺍﻜﺭﺓ

PA+2

ﻭ

PA+3

The LES instruction is used to load a specified register with the contents of PA and PA+1

memory locations, and load LES with the contents of PA+2 and PA+3 memory locations.

ﺍﻥ ﺍﻴﻌﺎﺯ

LES

ﻴﺴﺘﺨﺩﻡ ﻓﻲ ﻋﻤﻠﻴﺔ ﺘﺤﻤﻴل ﻤﺴﺠل ﻤﻌﻴﻥ ﺒﻤﺤﺘﻭﻯ ﻤﻭﺍﻗﻊ ﺍﻟﺫﺍﻜﺭﺓ

ﻭ

PA+1

ﻭﺘﺤﻤﻴل

ﺒﻤﺤﺘﻭﻯ ﻤﻭﺍﻗﻊ

ﺍﻟﺫﺍﻜﺭﺓ

PA+2

ﻭ

PA+3

Example 1 : Assuming that BX=20H ,DI=1000H , DS=1200H and the following memory

contents:

12204

12203

12202

12201

12200

Memory

Content

What result is produced in the destination operand by execution the following instruction?

a- LEA SI,[DI+BX+5] b- LDS SI,[200]

Solution :

a- EA =1000+20+5=1025 then (SI)=1025

b- PA=DS:EA=DS*10+EA=1200*10+200=12200

∴

(SI)=AA11H and (DS)=FFEEH