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Addressing mode Mnemonic Segment for memory access
Symbolic representation
IMMEDIATE
Addressing mode Mnemonic Segment for memory access
Symbolic representation
IMMEDIATE MOV AX,1000
Addressing mode Mnemonic Segment for memory access
Symbolic representation
IMMEDIATE MOV AX,1000 CODE
Addressing mode Mnemonic Segment for memory access
Symbolic representation
IMMEDIATE MOV AX,1000 CODE AH<=10, AL<=00
Addressing mode Mnemonic Segment for memory access
Symbolic representation
IMMEDIATE MOV AX,1000 CODE AH<=10, AL<=00
REGISTER
Addressing mode Mnemonic Segment for memory access
Symbolic representation
IMMEDIATE MOV AX,1000 CODE AH<=10, AL<=00
REGISTER MOV DX,CX
Addressing mode Mnemonic Segment for memory access
Symbolic representation
IMMEDIATE MOV AX,1000 CODE AH<=10, AL<=00
REGISTER MOV DX,CX WITHIN THE CPU
Addressing mode Mnemonic Segment for memory access
Symbolic representation
IMMEDIATE MOV AX,1000 CODE AH<=10, AL<=00
REGISTER MOV DX,CX WITHIN THE CPU
DX<=CX
Addressing mode Mnemonic Segment for memory access
Symbolic representation
IMMEDIATE MOV AX,1000 CODE AH<=10, AL<=00
REGISTER MOV DX,CX WITHIN THE CPU
DX<=CX
DIRECT
Addressing mode Mnemonic Segment for memory access
Symbolic representation
IMMEDIATE MOV AX,1000 CODE AH<=10, AL<=00
REGISTER MOV DX,CX WITHIN THE CPU
DX<=CX
DIRECT MOV AL,[2000]
Addressing mode Mnemonic Segment for memory access
Symbolic representation
IMMEDIATE MOV AX,1000 CODE AH<=10, AL<=00
REGISTER MOV DX,CX WITHIN THE CPU
DX<=CX
DIRECT MOV AL,[2000] DATA
Addressing mode Mnemonic Segment for memory access
Symbolic representation
IMMEDIATE MOV AX,1000 CODE AH<=10, AL<=00
REGISTER MOV DX,CX WITHIN THE CPU
DX<=CX
DIRECT MOV AL,[2000] DATA AL<=[2000]
Addressing mode Mnemonic Segment for memory access
Symbolic representation
IMMEDIATE MOV AX,1000 CODE AH<=10, AL<=00
REGISTER MOV DX,CX WITHIN THE CPU
DX<=CX
DIRECT MOV AL,[2000] DATA AL<=[2000]
REGISTER INDIRECT
Addressing mode Mnemonic Segment for memory access
Symbolic representation
IMMEDIATE MOV AX,1000 CODE AH<=10, AL<=00
REGISTER MOV DX,CX WITHIN THE CPU
DX<=CX
DIRECT MOV AL,[2000] DATA AL<=[2000]
REGISTER INDIRECT
MOV AX,[SI]
JMP [DI]
INC BYTEPTR[BP]
DEC WORDPTR[BX]
Addressing mode Mnemonic Segment for memory access
Symbolic representation
IMMEDIATE MOV AX,1000 CODE AH<=10, AL<=00
REGISTER MOV DX,CX WITHIN THE CPU
DX<=CX
DIRECT MOV AL,[2000] DATA AL<=[2000]
REGISTER INDIRECT
MOV AX,[SI] DATA
JMP [DI] DATA
INC BYTEPTR[BP] STACK
DEC WORDPTR[BX] DATA
Addressing mode Mnemonic Segment for memory access
Symbolic representation
IMMEDIATE MOV AX,1000 CODE AH<=10, AL<=00
REGISTER MOV DX,CX WITHIN THE CPU
DX<=CX
DIRECT MOV AL,[2000] DATA AL<=[2000]
REGISTER INDIRECT
MOV AX,[SI] DATA AL<=[SI]AH<=[SI+1]
JMP [DI] DATA
INC BYTEPTR[BP] STACK
DEC WORDPTR[BX] DATA
Addressing mode Mnemonic Segment for memory access
Symbolic representation
IMMEDIATE MOV AX,1000 CODE AH<=10, AL<=00
REGISTER MOV DX,CX WITHIN THE CPU
DX<=CX
DIRECT MOV AL,[2000] DATA AL<=[2000]
REGISTER INDIRECT
MOV AX,[SI] DATA AL<=[SI]AH<=[SI+1]
JMP [DI] DATA IP <={[DI+1] [DI]}
INC BYTEPTR[BP] STACK
DEC WORDPTR[BX] DATA
Addressing mode Mnemonic Segment for memory access
Symbolic representation
IMMEDIATE MOV AX,1000 CODE AH<=10, AL<=00
REGISTER MOV DX,CX WITHIN THE CPU
DX<=CX
DIRECT MOV AL,[2000] DATA AL<=[2000]
REGISTER INDIRECT
MOV AX,[SI] DATA AL<=[SI]AH<=[SI+1]
JMP [DI] DATA IP <={[DI+1] [DI]}
INC BYTEPTR[BP] STACK [BP]<=[BP]+1
DEC WORDPTR[BX] DATA
Addressing mode Mnemonic Segment for memory access
Symbolic representation
IMMEDIATE MOV AX,1000 CODE AH<=10, AL<=00
REGISTER MOV DX,CX WITHIN THE CPU
DX<=CX
DIRECT MOV AL,[2000] DATA AL<=[2000]
REGISTER INDIRECT
MOV AX,[SI] DATA AL<=[SI]AH<=[SI+1]
JMP [DI] DATA IP <={[DI+1] [DI]}
INC BYTEPTR[BP] STACK [BP]<=[BP]+1
DEC WORDPTR[BX] DATA {[BX+1][BX]}<={[BX+1][BX]} – 1
Addressing mode Mnemonic Segment for memory access
Symbolic representation
RELATIVE INDEXED(RELATIVE REGISTER INDIRECT)
MOV AX,[SI+6]
JMP [DI+6]
RELATIVE BASED(RELATIVE REGISTER INDIRECT)
MOV AX,[BP+2]
JMP [BX+2]
Addressing mode Mnemonic Segment for memory access
Symbolic representation
RELATIVE INDEXED(RELATIVE REGISTER INDIRECT)
MOV AX,[SI+6] DATA
JMP [DI+6] DATA
RELATIVE BASED(RELATIVE REGISTER INDIRECT)
MOV AX,[BP+2] STACK
JMP [BX+2] DATA
Addressing mode Mnemonic Segment for memory access
Symbolic representation
RELATIVE INDEXED(RELATIVE REGISTER INDIRECT)
MOV AX,[SI+6] DATA AL<=[SI+6], AH<=[SI+7]
JMP [DI+6] DATA
RELATIVE BASED(RELATIVE REGISTER INDIRECT)
MOV AX,[BP+2] STACK
JMP [BX+2] DATA
Addressing mode Mnemonic Segment for memory access
Symbolic representation
RELATIVE INDEXED(RELATIVE REGISTER INDIRECT)
MOV AX,[SI+6] DATA AL<=[SI+6], AH<=[SI+7]
JMP [DI+6] DATA IP <={[DI+7] [DI+6]}
RELATIVE BASED(RELATIVE REGISTER INDIRECT)
MOV AX,[BP+2] STACK
JMP [BX+2] DATA
Addressing mode Mnemonic Segment for memory access
Symbolic representation
RELATIVE INDEXED(RELATIVE REGISTER INDIRECT)
MOV AX,[SI+6] DATA AL<=[SI+6], AH<=[SI+7]
JMP [DI+6] DATA IP <={[DI+7] [DI+6]}
RELATIVE BASED(RELATIVE REGISTER INDIRECT)
MOV AX,[BP+2] STACK AL<=[BP+2], AH<=[BP+3]
JMP [BX+2] DATA
Addressing mode Mnemonic Segment for memory access
Symbolic representation
RELATIVE INDEXED(RELATIVE REGISTER INDIRECT)
MOV AX,[SI+6] DATA AL<=[SI+6], AH<=[SI+7]
JMP [DI+6] DATA IP <={[DI+7] [DI+6]}
RELATIVE BASED(RELATIVE REGISTER INDIRECT)
MOV AX,[BP+2] STACK AL<=[BP+2], AH<=[BP+3]
JMP [BX+2] DATA IP <={[BP+3] [BP+2]}
Addressing mode Mnemonic Segment for memory access
Symbolic representation
BASED AND INDEXED
MOV AX,[BX+SI]
JMP [BX+DI]
INC BYTEPTR[BP+SI]
DEC WORDPTR[BP+DI]
Addressing mode Mnemonic Segment for memory access
Symbolic representation
BASED AND INDEXED
MOV AX,[BX+SI] DATA
JMP [BX+DI] DATA
INC BYTEPTR[BP+SI] STACK
DEC WORDPTR[BP+DI]
STACK
Addressing mode Mnemonic Segment for memory access
Symbolic representation
BASED AND INDEXED
MOV AX,[BX+SI] DATA AL<=[BX+SI], AH<=[BX+SI+1]
JMP [BX+DI] DATA
INC BYTEPTR[BP+SI] STACK
DEC WORDPTR[BP+DI]
STACK
Addressing mode Mnemonic Segment for memory access
Symbolic representation
BASED AND INDEXED
MOV AX,[BX+SI] DATA AL<=[BX+SI], AH<=[BX+SI+1]
JMP [BX+DI] DATA IP <={[BX+DI+1] [BX+DI]}
INC BYTEPTR[BP+SI] STACK
DEC WORDPTR[BP+DI]
STACK
Addressing mode Mnemonic Segment for memory access
Symbolic representation
BASED AND INDEXED
MOV AX,[BX+SI] DATA AL<=[BX+SI], AH<=[BX+SI+1]
JMP [BX+DI] DATA IP <={[BX+DI+1] [BX+DI]}
INC BYTEPTR[BP+SI] STACK [BP+SI]<=[BP+SI]+1
DEC WORDPTR[BP+DI]
STACK
Addressing mode Mnemonic Segment for memory access
Symbolic representation
BASED AND INDEXED
MOV AX,[BX+SI] DATA AL<=[BX+SI], AH<=[BX+SI+1]
JMP [BX+DI] DATA IP <={[BX+DI+1] [BX+DI]}
INC BYTEPTR[BP+SI] STACK [BP+SI]<=[BP+SI]+1
DEC WORDPTR[BP+DI]
STACK {[BP+DI+1][BP+DI]} <={[BP+DI+1][BP+DI]} - 1
Addressing mode Mnemonic Segment for memory access
Symbolic representation
BASED AND INDEXED WITH DISPLACEMENT (RELATIVE BASED AND INDEXED]
MOV AX,[BX+SI+5]
JMP [BX+DI+5]
INC BYTEPTR[BP+SI+5]
DEC WORDPTR[BP+DI+5]
Addressing mode Mnemonic Segment for memory access
Symbolic representation
BASED AND INDEXED WITH DISPLACEMENT (RELATIVE BASED AND INDEXED]
MOV AX,[BX+SI+5] DATA
JMP [BX+DI+5] DATA
INC BYTEPTR[BP+SI+5]
STACK
DEC WORDPTR[BP+DI+5]
STACK
Addressing mode Mnemonic Segment for memory access
Symbolic representation
BASED AND INDEXED WITH DISPLACEMENT (RELATIVE BASED AND INDEXED]
MOV AX,[BX+SI+5] DATA AL<=[BX+SI+5], AH<=[BX+SI+6]
JMP [BX+DI+5] DATA
INC BYTEPTR[BP+SI+5]
STACK
DEC WORDPTR[BP+DI+5]
STACK
Addressing mode Mnemonic Segment for memory access
Symbolic representation
BASED AND INDEXED WITH DISPLACEMENT (RELATIVE BASED AND INDEXED]
MOV AX,[BX+SI+5] DATA AL<=[BX+SI+5], AH<=[BX+SI+6]
JMP [BX+DI+5] DATA IP <={[BX+DI+6] [BX+DI+5]}
INC BYTEPTR[BP+SI+5]
STACK
DEC WORDPTR[BP+DI+5]
STACK
Addressing mode Mnemonic Segment for memory access
Symbolic representation
BASED AND INDEXED WITH DISPLACEMENT (RELATIVE BASED AND INDEXED]
MOV AX,[BX+SI+5] DATA AL<=[BX+SI+5], AH<=[BX+SI+6]
JMP [BX+DI+5] DATA IP <={[BX+DI+6] [BX+DI+5]}
INC BYTEPTR[BP+SI+5]
STACK [BP+SI+5]<=[BP+SI+5]+1
DEC WORDPTR[BP+DI+5]
STACK
Addressing mode Mnemonic Segment for memory access
Symbolic representation
BASED AND INDEXED WITH DISPLACEMENT (RELATIVE BASED AND INDEXED]
MOV AX,[BX+SI+5] DATA AL<=[BX+SI+5], AH<=[BX+SI+6]
JMP [BX+DI+5] DATA IP <={[BX+DI+6] [BX+DI+5]}
INC BYTEPTR[BP+SI+5]
STACK [BP+SI+5]<=[BP+SI+5]+1
DEC WORDPTR[BP+DI+5]
STACK {[BP+DI+6][BP+DI+5]} <={[BP+DI+6][BP+DI+5]} - 1
Addressing mode Mnemonic Segment for memory access
Symbolic representation
STRING MOVSB
IMPLICIT CLD
Addressing mode Mnemonic Segment for memory access
Symbolic representation
STRING MOVSB EXTRA, DATA
IMPLICIT CLD WITHIN THE CPU
Addressing mode Mnemonic Segment for memory access
Symbolic representation
STRING MOVSB EXTRA, DATA ES:[DI]<=DS:[SI]IF DF=0, INCREMENT SI AND DI BY 1IF DF =1, DECREMENT SI AND DI BY 1
IMPLICIT CLD WITHIN THE CPU
DF = 0
IDENTIFY THE ADDRESSING MODE
MOV AH,47MOV AH,[BP+2]MOV AL,[BP+SI]STDMOV AH,BLMOV DX,[2002]
Problem statement – clear the contents of three memory location
Memory content location62380 0062381 0062382 00
8086 Sample programs MOV AX,6000H move 6000h into AX MOV ES,AX move AX contents into ES MOV DI,2380H move 2380H into DI MOV CX,0003H move 0003H into CX MOV AL,00H move 00H into ALAgain MOV [DI],AL AL => ES:[DI} INC DI Increment the contents of DI LOOP AGAIN dec CX, and if CX is NZ go to again HLT Halt
8086 Sample programs MOV AX,6000H move 6000h into AX MOV ES,AX move AX contents into ES MOV DI,2380H move 2380H into DI CLD clear the direction flag MOV CX,0003H move 0003H into CX MOV AL,00H move 00H into ALREP STOSB AL => ES:[DI]and increment DI (rep this CX times) HLT Halt
(CX=0003h) (AL = 00h)(DI=2380h)(ES=6000h)
• 1st time REP STOSBAL =>ES:[DI] i.e. 00=> [62380]h and DI = 2381h
CX=0002h• 2ND time REP STOSB
AL =>ES:[DI] i.e. 00=> [62381]h and DI = 2382hCX=0001h
• 3RD time REP STOSBAL =>ES:[DI] i.e. 00=> [62382]h and DI = 2383h
CX=0000h• 4TH Time will not happen cos CX = 0000h
REP LOOPPREFIX INSTRUCTIONUSED ONLY BEFORE STRING INSTRUCTION
USED ANYWHERE
USED TO REPEAT ONLY THAT STRING INSTRUCTION
USED TO REPEAT SERIES OF INSTRUCTION
String instructionsSTOSB AL=>ES:[DI] After string opr, if DF = 0, then DI is incremented by 1and viceversa LODSB AL<=DS:[SI]After string opr, if DF = 0, then SI is incremented by 1and viceversa MOVSB DS:[SI]=>ES:[DI]After string opr, if DF = 0, then SI and DI is incremented by 1and viceversa SCASB AL – ES:[DI]After string opr, if DF = 0, then DI is incremented by 1and viceversa CMPSB DS:[SI] – ES:[DI]After string opr, if DF = 0, then SI and DI is incremented by 1and viceversa
Problem statement block transfer
Transfer contents of 52500 to 62500 and 52501 to 62501
Block transferMOV AX,5000 HMOV DS,AXMOV SI,2500HMOV AX,6000HMOV DI,2500HCLDMOV CX,0002HREP MOVSB DS:[SI] =>ES:[DI] and increment DI and SI (rep this CX times)
HLT
(CX=0002h) (DS=5000h)(SI=2500h)(DI=2500h)(ES=6000h)
• 1st time REP MOVSB DS:[SI] =>ES:[DI] i.e. [52500]=>[62500]
SI =2501 and DI = 2501CX=0001h
• 2ND time REP MOVSBDS:[SI] =>ES:[DI] i.e. [52501]=>[62501]
SI =2502 and DI = 2502CX=0000h
• 3rd Time will not happen cos CX = 0000h
8086 sample programs
When both the numbers are positive(+03)h x (+02)h = (+06)hMOV AL,03HMOV BL,02HIMUL BLResult: (+0006)h => AX
8086 sample programsWhen both the numbers are not positive(+03)h x (-02)h = (-06)h2’s complement of 02 = 1’s complement of 00000010 + 1=11111110 = FEhMOV AL,03HMOV BL,FEHIMUL BLResult: (FFFA)h => AX(FFFA)h is actually –(0006)h
8086 sample programs
(+09)h / (-02)h MOV AX,0009HMOV BL,FEHIDIV BLResult: (01FC)h => AX01 =>AH is the remainderFC =>AL is the quotient (-04)h
8086 sample programs
(-09)h / (+02)h MOV AX,FFF7HMOV BL,02HIDIV BLResult: (FFFC)h => AXFF =>AH is the remainder (-01)hFC =>AL is the quotient (-04)h
MOV AX,5000 H MOV DS,AXMOV SI,2500HMOV AX,6000HMOV ES,AXMOV DI,2500HCLDMOV CX,0004HREPNE CMPSB DS:[SI] - ES:[DI] and increment DI and SI (REPNE) HLT
MEMORY SOURCE
CONTENT MEMORYDEST
CONTENT
52500 42 62500 98
52501 45 62501 34
52502 34 62502 34
52503 23 62503 23
(CX=0004h) (DS=5000h)(SI=2500h)(DI=2500h)(ES=6000h)• 1st time REPNE CMPSB
DS:[SI] - ES:[DI] i.e. [52500]-[62500] i.e. 42-98(NE) SI =2501 and DI = 2501
CX=0003h(this is cos of REP prefix)• 2ND time REP CMPSB DS:[SI] - ES:[DI] i.e. [52501]-[62501] i.e. 45-34(NE) SI =2502 and DI = 2502
CX=0002h(this is cos of REP prefix)• 3rd Time REPNE CMPSBDS:[SI] - ES:[DI] i.e. [52502]-[62502] i.e. 34-34(E) SI =2503 and DI = 2503
CX=0001h(this is cos of REP prefix)• 4TH Time REPNE CMPSB will not happen cos locations are no
longer NE
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