Instruction set of 8086 Microprocessor

YASH PAL,

Instruction set of 8086 Microprocessor – Each microprocessor has its own instruction set. The instructions of the Intel 8086 microprocessor are much more powerful than those of the 8085 microprocessor. The 8085 microprocessor is a one-address microprocessor because one operand is given in the instruction, and the other is supposed to be present in the accumulator. The 8086 is a general-purpose register-type microprocessor. Both operands can be specified in one instruction.

Types of 8086 Instruction Set

The 8086 instruction set is categorized as follows.

  1. Data Copy/Transfer instructions
  2. Arithmetic instructions
  3. Logical instructions
  4. Shift and Rotate instructions
  5. Branch instructions
  6. Loop instructions
  7. Flag (Bit) Manipulation Instructions
  8. Processor Control Instructions
  9. String Instructions

Below is the overview of the instructions of the Intel 8086 microprocessor.

Data Copy/Transfer Instructions of 8086

These types of instructions are used to transfer data from the source operand to the destination operand.

  1. MOV – Move the data
  2. PUSH – Push the data into the stack
  3. POP – Pop the data from the stack
  4. XCHG – Exchange
  5. IN – Input from
  6. OUT – Output to
  7. XLAT – Translate byte to AL
  8. LEA – Load Effective address to Register
  9. LDS – Load effective address to DS
  10. LES – Load effective address to ES
  11. LAHF – Load AH with FlagsL
  12. SAHF – Store AH into the FlagL
  13. PUSH F – Push flags to stack
  14. POP F – Pop flags from the stack

Arithmetic Instructions of 8086

All the instructions for performing arithmetic operations belong to this category.

  1. ADD – Addition
  2. ADC – Addition with carry
  3. INC – Increment by one
  4. DEC – Decrement by one
  5. SUB – Subtraction
  6. SBB – Subtraction with borrow
  7. MUL – Multiply (unsigned)
  8. IMUL – Signed Integer multiply
  9. DIV – Divide (unsigned)
  10. IDIV – Signed Integer Divide
  11. AAA – ASCII adjust for addition
  12. DAA – Decimal adjust for Addition
  13. AAS – ASCII Adjust for subtract
  14. DAS – Decimal adjust for subtract
  15. AAM – ASCII adjust for Multiply
  16. AAD – ASCII adjust for Divide
  17. CMP – Compare
  18. CBW – Convert byte to word
  19. CWD – Convert words to double words

Logical Instructions

All the instructions performing logical operations belong to this category.

  1. NOT – 1’s complement
  2. NEG – 2’s Complement
  3. AND – AND operation
  4. OR – OR operation
  5. XOR – Exclusive OR operation
  6. TEST – And operation without storing the result.

Shift and Rotate Instructions

These instructions involve the bitwise shifting or rotation in either direction, with or without a count in CL.

  1. SHL/SAL – Shift Logical/Arithmetic left
  2. SHR – Shift Logical Right
  3. SAR – Shift arithmetic Right
  4. ROL – Rotate left without carry
  5. ROR – Rotate right without carry
  6. RCL – Rotate left with carry
  7. RCR – Rotate right with carry

Branch Instructions

These instructions transfer control of execution to the specified address. All the calls, jump, interrupt and return instructions belong to this class.

  1. CALL – Call
  2. JUMP – Unconditional jump
  3. RET – Return
  4. JE/JZ – Jump on equal zero
  5. JNE/JNZ – Jump on not equal/not zero
  6. JL/JNGE – Jump on less/not greater than and equal
  7. JNL/JGE – Jump on not less/ greater and equal
  8. JNLE/JG – Jump on not less equal/on greater
  9. JLE/JNG – Jump on less or equal/not greater
  10. JB/JNAE/JC – Jump on below/not above equal/on carry
  11. JBE/JNA – Jump on below or equal/not above
  12. JNB/JAE/JNE – Jump on not below/above or equal/on no carry
  13. JNBE/JA – Jump on not below or equal/on above
  14. JP/JPE – Jump on parity/even parity
  15. JNP/JPO – Jump on parity/odd parity
  16. JO – Jump on overflow
  17. JNO – Jump on not overflow
  18. JS – Jump on signed (Negative)
  19. JNS – Jump on not signed (Positive)
  20. JCXZ – Jump on CX = zero
  21. INTn – Interrupt type n
  22. INTO – Interrupt on overflow
  23. IRET – Interrupt return

Loop Instructions

8086 instruction set also provides such instruction which does the all operations of decrementing the counter, checking the condition, and, according to that, branching, the sequence or not in a single instruction.

  1. LOOP – Loop CX times
  2. LOOPZ/LOOPE – Loop CX times while zero/equal
  3. LOOPNZ/LOOP NE – Loop CX times while not zero/not equal

Flag (Bit) Manipulation Instructions

All the instructions that directly affect the flag register come under the group of instructions.

  1. CLC – Clear carry Flag
  2. CMC – Component carry flag
  3. STC – Set Carry flag
  4. CLD – Clear Direction flag
  5. STD – Set Direction flag
  6. CLI – Clear Interrupt flag
  7. STI – Set Interrupt flag

Processor Control Instructions

These instructions control the machine status

  1. HLT – Halt
  2. WAIT – Wait
  3. ESC – Escape to external device
  4. LOCk – Bus Lock prefix

String Instructions

These instructions involve various string manipulation operations.

  1. REP – Repeat prefix until CX = 0
  2. REPE/REPZ – Repeat prefix until CX = 0 or on equal/zero
  3. REPNE/REPNZ – Repeat prefix until CX = 0 or on not equal/not zero
  4. MOVS B/W – Move string byte/word
  5. CMPS B/W – Compare string byte/word
  6. SCAS B/W – Scan String Byte/Word
  7. LODS B/W – Load String Byte/Word
  8. STOS B/W – Store String Byte/Word
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