instruction set of 8086

1 Assembly Language Microprocessors I 2 Assembly Language Microprocessors I Data Movement ⎯ Abbreviations src = source (‫)מקור‬ dest = destination (‫)יעד‬ acc = accumulator (AL or AX) 8086 Instruction Set PTR = pointer (‫)מצביע‬ DWORD = double word (32 bits) . = concatenation (AX = AH.AL) Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land 3 Assembly Language Microprocessors I 4 Assembly Language Microprocessors I Data Movement ⎯ Conventions Data Movement ⎯ Scope AX ← BX BYTE PTR[1000] Copy BX to AX Memory byte at address 1000 REGS[AX] ←⎯⎯⎯⎯⎯ REGS[BX] ⎯ WORD PTR[1000] 16- bits Memory word (2 bytes) at address 1000 and address 1001 AL ← [1000] DWORD PTR[1000] Copy memory byte at address 1000 to AL Memory dword (4 bytes) at addresses 1000, 1001, 1002, 1003 REGS[AL] ←⎯⎯⎯⎯ MEM[1000]⎯ 8- bits AX ← [BX] AL ← [BX] AX ← WORD PTR[BX] Copy memory byte at address stored in BX to AL AL ← [BX] and AH ← [BX+1] REGS[AL] ←8 MEM[ REGS[BX] ] REGS[AL] ←⎯⎯⎯⎯ MEM[ REGS[BX] ] ⎯ REGS[AH] ←8 MEM[ REGS[BX] + 1 ] 8- bits Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land

5 Assembly Language Microprocessors I 6 Assembly Language Microprocessors I How are Assembly Instructions Used? Simple Assembly Program Instructions Instructions written as list MOV dest, src ; dest ← src MOV DX, 1122 ; DX ← 1122 ADD dest, src ; dest ← dest + src MOV AX, [3344] ; AX ← [DS:3344] ADD AX, DX ; AX ← AX + DX MOV BX, 5566 ; BX ← 5566 Program set-up by Operating System MOV SI, 0008 ; SI ← 0008 1. Load program and data into memory ADD AX, [BX+SI] ; AX ← AX + [DS:BX+SI] 2. Set CS, DS, SS, ES, IP, SP to program locations MOV [BX], AX ; [DS:BX] ← AX 3. Set AX = BX = CX = DX = SI = DI = BP = 0 4. Load and run program from CS:IP CPU Fetches next instruction in list Decodes fetched instruction Executes decoded instruction Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land 7 Assembly Language Microprocessors I 8 Assembly Language Microprocessors I MOV Stack Organization MOV dest, src dest ← src 8086 provides user stack 12 MOV AX, 1234 REGS[AX] ←⎯⎯⎯⎯⎯ 1234 34 Full 16-bits Last In First Out (LIFO) buffer 56 Part MOV AX, BX REGS[AX] ←⎯⎯⎯⎯⎯ REGS[BX] SS:SP points to top of stack 78 of 16-bits Last filled location in stack 9A Stack REGS[AX] ←⎯⎯⎯⎯⎯ MEM[1234] SP → BC Stack expands down MOV AX, [1234] 16-bits REGS[AL] ←⎯⎯⎯⎯⎯ MEM[1234] Fills from higher to lower addresses 8-bits PUSH src REGS[AH] ←⎯ ⎯⎯⎯⎯ MEM[1235] copies scr to top of stack Empty 8-bits Part SP ← SP - 2 MOV AL, [1234] REGS[AL] ←⎯⎯⎯⎯⎯ MEM[1234] of 8-bits SS:SP ←⎯⎯⎯ src 16-bits ⎯ Stack MOV AX, [BX] REGS[AX] ←⎯⎯⎯⎯⎯ MEM[ REGS[BX] ] POP dest 16-bits moves top of stack to dest SS → MOV AX, [BX+SI] REGS[AX] ←⎯⎯⎯⎯⎯ MEM[ REGS[BX] + REGS[SI] ] 16-bits dest ←⎯⎯⎯ SS:SP 16-bits ⎯ MOV AX, [BX+SI+1234] REGS[AX] ←⎯⎯⎯⎯⎯ MEM[ REGS[BX] + REGS[SI] + 1234 ] SP ← SP + 2 16-bits Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land

9 Assembly Language Microprocessors I 10 Assembly Language Microprocessors I PUSH PUSH DS = 1122 12 DS = 1122 12 34 34 ES = 3344 ES = 3344 56 Full 56 78 Part 78 Full PUSH DS SP ← SP – 2 9A of PUSH DS SP ← SP – 2 9A Part [SS:SP] ← DS BC Stack MEM[SS:SP] ← DS BC of 11 11 Stack SP → 22 22 PUSH ES SP ← SP – 2 33 MEM[SS:SP] ← ES SP → 44 Empty Part Empty of Part Stack of Stack SS → SS → Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land 11 Assembly Language Microprocessors I 12 Assembly Language Microprocessors I POP PUSHA / POPA DS = 1122 12 PUSHA POPA 34 Saves registers to stack Restores registers ES = 3344 56 Full Equivalent to executing Equivalent to executing 78 Part POP CS CS ← [SS:SP] 9A of PUSH AX POP DI SP ← SP + 2 BC Stack PUSH CX POP SI 11 PUSH DX POP BP SP → 22 PUSH BX POP SP (value is CS = 3344 33 discarded) PUSH SP (value of SP 44 Empty before PUSH AX) POP BX Part PUSH BP POP DX of PUSH SI POP CX Stack PUSH DI POP AX SS → Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land

13 Assembly Language Microprocessors I 14 Assembly Language Microprocessors I Segment Override Bitwise Logical Operations dest ← not dest CS: MOV [BP],CX CS:[BP] ← CX NOT dest NOT 11001111 → 00110000 ES: MOV [BP],CX ES:[BP] ← CX DS: MOV [BP],CX DS:[BP] ← CX dest ← dest AND src AND dest, src 10110000 AND 11001111 → 10000000 SS: MOV [BP],CX SS:[BP] ← CX dest ← dest OR src OR dest, src 10110000 OR 11001111 → 11111111 dest ← dest XOR src XOR dest, src 10110000 XOR 11001111 → 01111111 TEST dest, src dest AND src ; update flags Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land 15 Assembly Language Microprocessors I 16 Assembly Language Microprocessors I Using Boolean Operations Unsigned Integers ; AX ← 0 n-bit number is usual binary representation n=3 XOR AX,AX 7 111 Represents value from 0 to 2n-1 6 110 5 101 Integers determined modulo 2n MOV AX,1122 ; AX ← 1122 4 100 Overflow 3 011 AND AX,00FF ; AX ← 0022 a + b > 2n-1 2 010 1 001 Carry Flag is set 0 000 MOV AX,1122 ; AX ← 1122 CF 3-Bit Integer TEST AX,8000 ; ZF ← 1 (tests high 0 111 + 001 order bit) 1 000 CF 3-Bit Integer MOV AX,0001 ; AX ← 0001 0 000 ; AX ← FFFE - 001 NOT AX 1 111 Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land

17 Assembly Language Microprocessors I 18 Assembly Language Microprocessors I Signed Numbers ⎯ 1 Signed Numbers ⎯ 2 n-bit number (2’s complement) Upper bit = 0 for positive numbers Represents value from -2n-1 to +2n-1-1 Upper bit = 1 for negative numbers Integers determined modulo 2n n=3 n=4 Overflow +7 0111 Carry-in not equal to carry-out at highest order … … +3 011 +3 0011 Overflow Flag is set +2 010 +2 0010 +1 001 +1 0001 0 000 0 0000 -1 111 -1 1111 -2 110 -2 1110 -3 101 -3 1101 -4 100 -4 1100 … … -8 1000 Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land 19 Assembly Language Microprocessors I 20 Assembly Language Microprocessors I Signed Numbers ⎯ 3 Data Conversion OF CO CI 3-Bit Integer Decimal CBW — convert byte to word with sign extension 111 -1 CWD — convert word to double with sign extension + 001 + 1 0 1 1 000 0 If AL < 80H, then AH ← 0 OF CO CI 3-Bit Integer Decimal 00000000 0xxxxxxx ← xxxxxxxx 0xxxxxxx 111 -1 CBW - 001 - 1 If AL > 7F, then AH ← FFH 0 0 0 110 -2 11111111 1xxxxxxx ← xxxxxxxx 1xxxxxxx OF CO CI 3-Bit Integer Decimal If AX < 8000H, then DX ← 0 011 3 CWD + 001 + 1 If AX > 7FFFH. then DX ← FFFFH 1 0 1 100 4 Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land

21 Assembly Language Microprocessors I 22 Assembly Language Microprocessors I Add/Subtract Long Integer Add/Sub Long integers in DX.AX and DI.SI ADD dest, src dest ← dest + src ADC dest, src dest ← dest + src + CF ADD AX, SI AX ← AX + SI SUB dest ,src dest ← dest - src CF ← carry ADC DX, DI DX ← DX + DI + CF SBB dest ,src dest ← dest - src - CF CF ← overflow INC dest dest ← dest + 1 DEC dest dest ← dest - 1 SUB AX, SI AX ← AX - SI CF ← borrow NEG dest dest ← 0 - dest SBB DX, DI DX ← DX - DI - CF CMP dest ,src dest - src; update flags CF ← overflow Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land 23 Assembly Language Microprocessors I 24 Assembly Language Microprocessors I Multiplication / Division Small Program MOV AX,1122 MUL BL AX ← AL*BL MUL source MOV BX,3344 MUL CX DX.AX ← AX*CX SUB BX,AX IMUL BL AX ← AL*BL MOV CX,0003 IMUL source IMUL CX IMUL CX DX.AX ← AX*CX AL ← AX / BL AX=0000 BX=0000 CX=0000 DIV BL AH ← AX % BL MOV AX,1122 AX=1122 BX=0000 CX=0000 DIV source AX ← DX.AX / CX MOV BX,3344 AX=1122 BX=3344 CX=0000 DIV CX SUB BX,AX AX=1122 BX=2222 CX=0000 DX ← DX.AX % CX MOV CX,0003 AX=1122 BX=2222 CX=0003 AL ← AX / BL IMUL CX AX=3366 BX=2222 CX=0003 IDIV BL AH ← AX % BL IDIV source AX ← DX.AX / CX IDIV CX DX ← DX.AX % CX Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land

25 Assembly Language Microprocessors I 26 Assembly Language Microprocessors I Shift Instructions Rotate Instructions SHR ROL — Rotate Left Shift Right SAR Shift Arithmetic Right ROR — rotate right Shift bits right with sign preservation RCL — rotate carry left SAL Shift Arithmetic Left Shift left, sign bit to CF OF = 1 if sign bit changes RCR — rotate carry right Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land 27 Assembly Language Microprocessors I 28 Assembly Language Microprocessors I String Instructions ⎯ 1 String Instructions ⎯ 2 Store ES:[DI] ← AL ES:[DI] ← DS:[SI] STOSB String If DF = 0, DI ← DI+1 Move If DF = 0, DI ← DI+1 Byte If DF = 1, DI ← DI-1 MOVSB String SI ← SI+1 Store ES:[DI] ← AL; ES:[DI+1] ← AH Byte If DF = 1, DI ← DI-1 STOSW String If DF = 0, DI ← DI+2 SI ← SI-1 Word If DF = 1, DI ← DI-2 ES:[DI] ← DS:[SI] ES:[DI+1] ← DS:[SI+1] Load AL ← DS:[SI] Move If DF = 0, DI ← DI+2 LODSB String If DF = 0, SI ← SI+1 MOVSW String SI ← Sl+2 Byte If DF = 1, SI ← SI-1. Word If DF = 1, DI ← DI-2 Load AL ← DS:[SI]: AH ← DS:[SI+1] SI ← SI-2 LODSW String If DF = 0, SI ← SI+2; AL-ES:[DI]; update flags Scan Word If DF = 1, SI ← SI-2 SCASB String If DF = 0, DI ← DI+1 Byte If DF = 1, DI ← DI-1 Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land

29 Assembly Language Microprocessors I 30 Assembly Language Microprocessors I String Instructions ⎯ 3 String Instructions ⎯ 4 AX-ES:[DI+l:DI]; Scan Update flags STOSB SCASW String If DF = 0, DI ← DI+2 REP STOSB CX ← CX - 1 Word If DF = I, DI ← DI-2 Repeat until CX = 0 DS:[SI]-ES:[DI]; Update flags STOSW Compare If DF = 0, DI ← DI+I REP STOSW CX ←CX - 1 CMPSB String SI ← SI+1 Repeat until CX = 0 Byte If DF = 1 , DI ← DI-1 SI ← SI-1 MOVSB DS:[SI+I:SI]-ES:[DI+1:DI]; REP MOVSB CX ← CX - 1 Update flags Repeat until CX = 0 Compare If DF = 0, DI ← DI+2 CMPSW String SI ← SI+2 MOVSW Word If DF = 1, DI ← DI-2 REP MOVSW CX ← CX - 1 SI ← SI-2 Repeat until CX = 0 Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land 31 Assembly Language Microprocessors I 32 Assembly Language Microprocessors I Working with Strings Branch Instructions PUSH ES ; SP ← SP – 2 Changes program execution order branch ; [SS:SP] ← ES Changes default IP to new IP under fall through program control PUSH DS ; SP ← SP – 2 Used to build for, while, if, short target ; [SS:SP] ← DS switch, … blocks short jump POP ES ; ES ← DS Target New IP after branch is executed near target ; SP ← SP + 2 near jump Fall-through MOV SI,0000 ; SI ← 0 Instruction below branch in program MOV DI,1000 ; DI ← 1000 listing MOV CX,200 ; CX ← 200 Default IP points to fall-through far target far REP MOVSB ; COPY 200 H BYTES FROM Displacement jump Displacement = Target IP – Fall-through IP ; DS:0000 – DS:01FF TO ; DS:1000 – DS:11FF Displacement > 0 is forward jump Displacement < 0 is backward jump Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land

33 Assembly Language Microprocessors I 34 Assembly Language Microprocessors I Jump Distance Jump Instruction branch Displacement = Target IP – Fall-through IP fall through JMP target ⇒ JMP near target (assembler chooses near or short) JMP FAR short target Near Short short jump JMP 1024 IP ←16 1024 Target in same code segment near target near JMP target JMP NEAR [1024] IP ←16 [1024] Displacement is byte jump -12810 = 80 ≤ displacement ≤ 7F = 12710 JMP NEAR [SI] IP ←16 [SI] CS ←16 1122 Near Jump JMP FAR 1122:3344 far target far IP ←16 3344 Target in same code segment jump CS ←16 [1026] Displacement is word (2 bytes) JMP far target JMP FAR [1024] IP ←16 [1024] -32,76810 = 8000 ≤ displacement ≤ 7FFF = 32,76710 CS ←16 [SI+2] JMP FAR [SI] Far Jump IP ←16 [SI] Target in different code segment Pointer is double word (4 bytes) Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land 35 Assembly Language Microprocessors I 36 Assembly Language Microprocessors I Conditional Jumps Unsigned Compare ⎯ 1 ALU operations set flags in the status word COMP ZF CF Conditional jumps test the flags and jump if flag is set A < B 0 1 Takes short target A = B 1 0 A > B 0 0 Mnemonic Condition Test JC Carry CF = 1 JE/JZ Equal/zero ZF = 1 A < B ⇒ CF =1 JP/JPE Parity / parity even PF = 1 A ≤ B ⇒ (ZF XOR CF) = 1 JNC Not carry CF = 0 A = B ⇒ ZF = 1 JNE/JNZ Not equal/not zero ZF = 0 A ≥ B ⇒ CF = 0 JNP/JPO Not Parity / parity odd PF = 0 A > B ⇒ (ZF XOR CF) = 0 (ZF = CF = 1 is impossible) Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land

37 Assembly Language Microprocessors I 38 Assembly Language Microprocessors I Unsigned Compare ⎯ 2 Signed Compare Condition Mnemonic Test Condition (Signed Operations) Mnemonic Test JG/JNLE Greater/not less nor equal (SF XOR OF) + ZF) = 0 (Unsigned Operations) JGE/JNL Greater or equal/not less (SF XOR OF) = 0 JA/JNBE Above/not below nor equal (CF XOR ZF) = 0 JL/JNGE Less/not greater nor equal (SF XOR OF) = 1 JAE/JNB Above or equal/not below CF = 0 JLE/JNG Less or equal/not greater ((SF XOR OF) + ZF) = 1 JB/JNAE Below/not above nor equal CF = 1 JO Overflow OF = 1 JBE/JNA Below or equal/not above CF XOR ZF = 1 JS Sign SF = 1 JNO Not overflow OF = 0 JNS Not sign SF = 0 Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land 39 Assembly Language Microprocessors I 40 Assembly Language Microprocessors I Simple Loop Loop Instruction 0100 XOR AX,AX ; zero accumulator (AX ← 0) LOOP short target LOOP 1024 CX ← CX - 1 0102 MOV BX,0001 ; BX ← 1 IF CX ≠ 0, JMP SHORT target 0105 ADD AX,BX ; add BX to accumulator LOOPZ short target LOOPZ 1024 CX ← CX - 1 0107 INC BX ; BX++ IF (CX ≠ 0) AND (ZF = 1), 0108 CMP BX,0005 ; set SF, ZF, OF according to value JMP SHORT target ; of BX – 5 LOOPNZ short target LOOPNZ 1024 CX ← CX - 1 010B JLE 0105 ; loop if ((SF XOR OF) + ZF) = 1 IF (CX ≠ 0) AND (ZF = 0), JMP SHORT target ; (BX ≤ 5) 0100 XOR AX,AX ; zero accumulator 0102 MOV CX,0005 ; CX ← 5 0105 ADD AX,CX ; add CX to accumulator 0107 LOOP 0105 ; CX-- and loop if CX > 0 Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land

41 Assembly Language Microprocessors I 42 Assembly Language Microprocessors I Call and Return Indirect Far Call stack stack CALL near target SP ← SP-2; [SP] ← IP; IP ← target SP CALL 1024 SP ← SP-2; [SP] ← IP; IP ← 1024 fall-through CS fall-through IP CALL [SI] SP ← SP-2; [SP] ← IP; IP ← [SI] SP CALL far target SP ← SP-2; [SP] ← CS; CS ← SEG; SP ← SP-2; [SP] ← IP; IP ← OFF CALL 1122:3344 SP ← SP-2; [SP] ← CS; CS ← 1122 IP = 1122 SP ← SP-2; [SP] ← IP; IP ← 3344 CS = 3344 CALL [SI] SP ← SP-2; [SP] ← CS; CS ← [SI+2] SP ← SP-2; [SP] ← IP; IP ← [SI] RET IP ← [SP]; SP ← SP+2 IP fall-through fall-through RETF IP ← [SP]; SP ← SP+2; CALL [SI] CALL [SI] CS CS ← [SP]; SP ← SP+2 44 44 33 33 22 22 SI 11 SI 11 DS DS Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land 43 Assembly Language Microprocessors I 44 Assembly Language Microprocessors I Software Interrupt (Trap) Software Interrupt Instructions Interrupts Program Flow INT type INT 20H SP ← SP-2; [SP] ← flags Transfers control to Interrupt Service Routine (ISR) IF ← 0; TF ← 0; ISR can be stored anywhere in memory SP ← SP-2; [SP] ← CS; CS ← [00083H:00082H]; Pointer to ISR stored in Interrupt Vector Table Table SP ← SP-2; [SP] ← IP; starts at 00000 IP ← [00081H:00080H] Each Vector is 4 bytes long (2×CS+2×IP) IRET none IRET IP ← [SP]; Vector 0 is at physical address 00000 SP ← SP+2; Vector 1 is at physical address 00004 CS ← [SP]; SP ← Vector 2 is at physical address 00008 SP+2; flags ← [SP]; ISR vector address is: INT_type×4 SP ← SP+2 Vector is: IP(L), IP(H), CS(L), CS(H) Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land

45 Assembly Language Microprocessors I 46 Assembly Language Microprocessors I Interrupt Hardware Interrupts stack stack INTR line on chip causes interrupt SP flags INT_type is on address lines A0 to A7 NMI line on chip causes non-maskable interrupt fall-through CS SP fall-through IP Cannot be masked (turned off) Always points to INT type 4 IP = 1122 A7 CS = 3344 A6 A5 A4 8086 A3 CPU A2 IP fall-through fall-through A1 INT 21 INT 21 A0 CS 44 44 33 33 INTR 22 22 00084 11 00084 11 NMI 00000 00000 Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land 47 Assembly Language Microprocessors I 48 Assembly Language Microprocessors I Processor Control Instructions More Data Movement Instructions STC CF ← I Set carry flag XCHG dest, src dest ↔ src CLC CF ← 0 Clear carry flag XCHG AX, BX AX ↔ BX CMC CF ← not(CF) Complement carry flag XCHG AL, AH AL ↔ AH STD DF ← 1 Set direction flag XCHG AX, [SI] AX ↔ [SI] CLD DF ← 0 Clear direction flag STI IF ← I Set interrupt flag LAHF AH ←⎯⎯⎯ flags (low byte) 8-bits CLI IF ← 0 Clear interrupt flag SAHF flags (low byte) ←⎯⎯⎯ AH 8-bits HLT None Halt WAIT None Enter wait state NOP None No operation Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land

49 Assembly Language Microprocessors I 50 Assembly Language Microprocessors I Translate — XLAT LEA Replaces AL with (AL+1)st value in a table Load Effective Address Uses AL as index into 256 byte table beginning at [BX] Similar to MOV Copies address (pointer) of memory location XLAT AL ← [BX+AL] Does not access memory MOV AL, 3 A3 XLAT 77 66 LEA dest, [EA] dest ←⎯⎯⎯ EA 16-bits ⎯ AL ← [BX+3] = 33 55 44 LEA AX, [1234] AX ←⎯⎯⎯ 1234 ⎯ BX+AL → 33 16-bits 22 REGS[AX] ←⎯⎯⎯ 1234 16-bits ⎯ 11 LEA CX, [SI+12] CX ←⎯⎯⎯ SI+12 ⎯ BX → 00 16-bits 97 REGS[CX] ←⎯⎯⎯ REGS[SI]+12 16-bits ⎯ 54 LEA DX, [BX + DI] DX ←⎯⎯⎯ BX + DI ⎯ 34 16-bits DS REGS[DX] ←⎯⎯⎯ REGS[BX]+ REGS[DI] 16-bits ⎯ Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land 51 Assembly Language Microprocessors I 52 Assembly Language Microprocessors I Moving Data Around LDS and LES MOV SI,1122 ; SI ← 1122 Loads a 32-bit logical address of type DS:EA or ES:EA MOV [0000],SI ; [DS:0000] ← 1122 MOV BX,3344 ; BX ← 3344 LDS dest, [EA] dest ←⎯⎯⎯ [EA] 16-bits ⎯ MOV [BX],SI ; [DS:3344] ← 1122 DS ←⎯⎯⎯ [EA + 2] 16-bits ⎯ MOV [BX+SI],BX ; [DS:4466] ← 3344 11 BX ←⎯⎯⎯ [SI] ⎯ 22 LEA BX,[BX+SI] ; BX ← 4466 LDS BX, [SI] 16-bits 33 DS ← 3344 MOV CS,[BX] ; CS ← [DS:4466] DS ←⎯⎯⎯ [SI+ 2] 16-bits ⎯ 44 55 MOV AX,[BX+2] ; AX ← [DS:4468] SI → 66 BX ← 5566 77 88 99 AA LES dest, [EA] dest ←⎯⎯⎯ [EA] 16-bits ⎯ DS ES ←⎯⎯⎯ [EA + 2] 16-bits ⎯ Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land

53 Assembly Language Microprocessors I 54 Assembly Language Microprocessors I Switching Data Tables Data Movement ⎯ I/O Operations ⎯ 1 /* DO ARITHMETIC WITH DS:BX = 1111:2222 */ 80x86 processors control an I/O signal on the memory bus /* SWITCH DATA TABLES */ MOV [SI], 4444 ; [SI] ← 4444 I/O signal is off to select processor access to RAM ; [SI+2] ← 3333 MOV [SI+2], 3333 I/O signal is on to select processor access to I/O bus PUSH DS ; SP ← SP – 2 ; [SS:SP] ← 1111 MOV selects RAM access PUSH BX ; SP ← SP – 2 IN and OUT select I/O access ; [SS:SP] ← 2222 LDS BX,[SI] ; BX ← 4444 ; DS ← 3333 AL or AX are always src/dest for I/O instructions /* DO ARITHMETIC WITH DS:BX = 3333:4444 */ /* SWITCH BACK TO FIRST DATA TABLE */ I/O address is called a port POP [SI] ; [SI] ← 2222 can range from 0000 H to FFFF H ; SP ← SP + 2 POP [SI+2] ; [SI+2] ← 1111 direct mode ⎯ 1 immediate byte address ; SP ← SP + 2 indirect mode ⎯ 2 address bytes in DX LDS BX,[SI] ; BX ← 2222 ; DS ← 1111 Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land 55 Assembly Language Microprocessors I 56 Assembly Language Microprocessors I Data Movement ⎯ I/O Operations ⎯ 2 Data Movement ⎯ I/O Instructions ⎯ 3 Memory Bus ‫אפיק זיכרון‬ IN AL,26H AL ← port 26H input byte from AL ← port 26H; ‫זיכרון‬ IN AX,26H port 0 ⎯ 255 ‫מטמון‬ ‫זיכרון ראשי‬ AH ← port 27H ‫מתאם‬ IN acc, port cache memory IN AL,DX AL ← port DX input byte from ‫אפיק‬ Data/Address Main Memory Bus AL ← port DX port 0 ⎯ 65,535 I/O (RAM) IN AX,DX Adapter AH ← port DX+1 (address in DX) ‫יהידת החישוב‬ ‫המרכזי‬ output byte to port DX ← AL Central Processing I/O Bus ‫אפיק קלט/פלט‬ OUT port, acc OUT DX,AX port 0 ⎯ 65,535 Unit (CPU) port DX+1 ← AH (address in DX) ‫בקר קלט/פלט‬ ‫בקר קלט/פלט‬ ‫בקר קלט/פלט‬ I/O Controller I/O Controller I/O Controller Disk ‫ממשק‬ ‫רשת תקשורת‬ ‫משתמש‬ communications network Spring 2009 Hadassah College Dr. Martin Land Spring 2009 Hadassah College Dr. Martin Land

http://www.campuskeeda.com	21
http://www.cetlylive.com	13
http://munnuz.com	3
http://www.slideshare.net	1
http://munnuz.co.cc	1

instruction set of 8086

by muneer.k on Jul 22, 2010

Accessibility

Categories

Tags

Upload Details

Usage Rights

5 Embeds 39

Statistics

instruction set of 8086 — Presentation Transcript