Chapter 17 80386 Instruction Set

This chapter presents instructions for the 80386 in alphabetical order. For each instruction, the forms are given for each operand combination, including object code produced, operands required, execution time, and a description. For each instruction, there is an operational description and a summary of exceptions generated.

• 17.1 Operand-Size and Address-Size Attributes
• 17.1.1 Default Segment Attribute
• 17.1.2 Operand-Size and Address-Size Instruction Prefixes
• 17.1.3 Address-Size Attribute for Stack
• 17.2 Instruction Format
• 17.2.1 ModR/M and SIB Bytes
• 17.2.2 How to Read the Instruction Set Pages
• 17.2.2.1 Opcode
• 17.2.2.2 Instruction
• 17.2.2.3 Clocks
• 17.2.2.4 Description
• 17.2.2.5 Operation
• 17.2.2.6 Description
• 17.2.2.7 Flags Affected
• 17.2.2.8 Protected Mode Exceptions
• 17.2.2.9 Real Address Mode Exceptions
• 17.2.2.10 Virtual-8086 Mode Exceptions
• 17.3 Instruction Set
• 17.3.A 'A' Instructions
• AAA -- ASCII Adjust after Addition
• AAD -- ASCII Adjust AX before Division
• AAM -- ASCII Adjust AX after Multiply
• AAS -- ASCII Adjust AL after Subtraction
• ADC -- Add with Carry
• ADD -- Add
• AND -- Logical AND
• ARPL -- Adjust RPL Field of Selector
• 17.3.B 'B' Instructions
• BOUND -- Check Array Index Against Bounds
• BSF -- Bit Scan Forward
• BSR -- Bit Scan Reverse
• BT -- Bit Test
• BTC -- Bit Test and Complement
• BTR -- Bit Test and Reset
• BTS -- Bit Test and Set
• 17.3.C 'C' Instructions
• CALL -- Call Procedure
• CBW/CWDE -- Convert Byte to Word/Convert Word to Doubleword
• CLC -- Clear Carry Flag
• CLD -- Clear Direction Flag
• CLI -- Clear Interrupt Flag
• CLTS -- Clear Task-Switched Flag in CR0
• CMC -- Complement Carry Flag
• CMP -- Compare Two Operands
• CMPS/CMPSB/CMPSW/CMPSD -- Compare String Operands
• CWD/CDQ -- Convert Word to Doubleword/Convert Doubleword to
• 17.3.D 'D' Instructions
• DAA -- Decimal Adjust AL after Addition
• DAS -- Decimal Adjust AL after Subtraction
• DEC -- Decrement by 1
• DIV -- Unsigned Divide
• 17.3.E 'E' Instructions
• ENTER -- Make Stack Frame for Procedure Parameters
• 17.3.H 'H' Instructions
• HLT -- Halt
• 17.3.I 'I' Instructions
• IDIV -- Signed Divide
• IMUL -- Signed Multiply
• IN -- Input from Port
• INC -- Increment by 1
• INS/INSB/INSW/INSD -- Input from Port to String
• INT/INTO -- Call to Interrupt Procedure
• IRET/IRETD -- Interrupt Return
• 17.3.J 'J' Instructions
• Jcc -- Jump if Condition is Met
• JMP -- Jump
• 17.3.L 'L' Instructions
• LAHF -- Load Flags into AH Register
• LAR -- Load Access Rights Byte
• LEA -- Load Effective Address
• LEAVE -- High Level Procedure Exit
• LGDT/LIDT -- Load Global/Interrupt Descriptor Table Register
• LGS/LSS/LDS/LES/LFS -- Load Full Pointer
• LLDT -- Load Local Descriptor Table Register
• LMSW -- Load Machine Status Word
• LOCK -- Assert LOCK# Signal Prefix
• LODS/LODSB/LODSW/LODSD -- Load String Operand
• LOOP/LOOPcond -- Loop Control with CX Counter
• LSL -- Load Segment Limit
• LTR -- Load Task Register
• 17.3.M 'M' Instructions
• MOV -- Move Data
• MOV -- Move to/from Special Registers
• MOVS/MOVSB/MOVSW/MOVSD -- Move Data from String to String
• MOVSX -- Move with Sign-Extend
• MOVZX -- Move with Zero-Extend
• MUL -- Unsigned Multiplication of AL or AX
• 17.3.N 'N' Instructions
• NEG -- Two's Complement Negation
• NOP -- No Operation
• NOT -- One's Complement Negation
• 17.3.O 'O' Instructions
• OR -- Logical Inclusive OR
• OUT -- Output to Port
• OUTS/OUTSB/OUTSW/OUTSD -- Output String to Port
• 17.3.P 'P' Instructions
• POP -- Pop a Word from the Stack
• POPA/POPAD -- Pop all General Registers
• POPF/POPFD -- Pop Stack into FLAGS or EFLAGS Register
• PUSH -- Push Operand onto the Stack
• PUSHA/PUSHAD -- Push all General Registers
• PUSHF/PUSHFD -- Push Flags Register onto the Stack
• 17.3.R 'R' Instructions
• RCL/RCR/ROL/ROR -- Rotate
• REP/REPE/REPZ/REPNE/REPNZ -- Repeat Following String Operation
• RET -- Return from Procedure
• 17.3.S 'S' Instructions
• SAHF -- Store AH into Flags
• SAL/SAR/SHL/SHR -- Shift Instructions
• SBB -- Integer Subtraction with Borrow
• SCAS/SCASB/SCASW/SCASD -- Compare String Data
• SETcc -- Byte Set on Condition
• SGDT/SIDT -- Store Global/Interrupt Descriptor Table Register
• SHLD -- Double Precision Shift Left
• SHRD -- Double Precision Shift Right
• SLDT -- Store Local Descriptor Table Register
• SMSW -- Store Machine Status Word
• STC -- Set Carry Flag
• STD -- Set Direction Flag
• STI -- Set Interrupt Flag
• STOS/STOSB/STOSW/STOSD -- Store String Data
• STR -- Store Task Register
• SUB -- Integer Subtraction
• 17.3.T 'T' Instructions
• TEST -- Logical Compare
• 17.3.V 'V' Instructions
• VERR, VERW -- Verify a Segment for Reading or Writing
• 17.3.W 'W' Instructions
• WAIT -- Wait until BUSY# Pin is Inactive (HIGH)
• 17.3.X 'X' Instructions
• XCHG -- Exchange Register/Memory with Register
• XLAT/XLATB -- Table Look-up Translation
• XOR -- Logical Exclusive OR

• Figure 17-1. 80386 Instruction Format
• Figure 17-2. ModR/M and SIB Byte Formats
• Figure 17-3. Bit Offset for BIT[EAX, 21]
• Figure 17-4. Memory Bit Indexing

• Table 17-1. Effective Size Attributes
• Table 17-2. 16-Bit Addressing Forms with the ModR/M Byte
• Table 17-3. 32-Bit Addressing Forms with the ModR/M Byte
• Table 17-4. 32-Bit Addressing Forms with the SIB Byte
• Table 17-5. Task Switch Times for Exceptions
• Table 17-6. 80386 Exceptions