EC 304 VLSI Module 1

 

Instruction set

·       Instruction is a binary pattern entered through an input device in memory to command the microprocessor to perform that specific function.

·      8 bit microprocessor can have  combinations of bit pattern.

·       8085 uses 246 combinations & which represent 74 instructions.

These 74 different instructions are known as instruction set

They are categorized into 5 different groups

·       Data transfer instruction

·       Arithmetic instructions

·       Logical instructions

·       Branch operations

·       Machine control instructions

Each instruction has two parts:

• Opcode – operation to be performed
• Operands – data to be operated

Notations used:

•     M – Memory location pointed by HL register pair
•     R – 8-bit register
•     Rs - Source register
•     Rd – Destination register

Data transfer Instructions

1.     MOV Rd , Rs                      E.g. MOV B , A

           Copy data from source register in to destination register

2. MVI R , 8-bit                       E.g. MVI B, 4FH

            Load 8-bit data into a register

3. LXI Rp, 16-bit                      E.g. LXI B ,2050H  

Load 16-bit number in a register pair

4.     OUT  8-bit                                  E.g. OUT 01H

       Write data from accumulator to an output port.

5. IN 8-bit                               E.g. IN 07H

      Read data byte from port address and store it in   accumulator

6.LDA 16-bit                          E.g. LDA 2050H

     Copy data byte into A from memory specified by 16-bit adrees.

7.  STA 16-bit                         E.g. STA 2070H

    Copy the data byte from A into memory specified by 16-  bit address.

8. LDAX Rp                           E.g. LDAX B

   Copy the data byte into A from memory specified by the   address in register pair

9.STAX Rp                             E.g. STAX D

   Copy the data byte from A into the memory specified by  address in register pair

10.MOV R, M                        E.g. MOV B,M

     Copy the data byte into register from the memory specified by the address in HL register  

    pair

11. MOV M, R                        E.g. MOV M,C

         Copy the data byte from the register into the memory specified by the address in HL  

        register pair

Arithmetical instructions

1.     ADD R                                          E.g. ADD B

        Add the content of specified register to the content of   accumulator & result stored in accumulator

2. ADI 8-bit                                        E.g. ADI 37H

        Add 8-bit data to the content of A

3. ADD M                                           E.g. ADD M

        Add content of memory to content of A. Memory  location specified in HL register pair

4. ADC R                                            E.g. ADC B

        Add the content of specified register to the content of  accumulator with carry& result stored in accumulator

5.  ACI 8-bit                                       E.g. ACI 37H

        Add 8-bit data to the content of A

6. ADC M                                           E.g. ADC M

        Add content of memory to content of A with carry. Memory location specified in HL register pair

7.SUB R                                              E.g. SUB B

      Subtract the content of specified register to the content   of  Accumulator & result stored in accumulator

8.  SUI 8-bit                                        E.g. SUI 37H

      Subtract 8-bit data to the content of A

9. SUB M                                            E.g. SUB M

        Subtract content of memory to content of A. Memory location specified in HL register pair                                                    

10. SBB R                                           E.g. SBB B

       Subtract the content of specified register to the content of accumulator with borrow& result stored in accumulator      

11. SBI 8-bit                                       E.g. SUI 37H

        Subtract 8-bit data to the content of A with borrow

12.  SBB M                                         E.g. SBB M

        Subtract content of memory to content of A with  borrow. Memory location specified in  

      HL register pair

13 INR R                                             E.g. INR D

        Increment the content of register

14. INR M                                           E.g. INR M

        Increment the content memory, which is specified in  HL register pair

15.  DCR R                                         E.g. DCR D

       Decrement the content of register

16. DCR M                                         E.g. DCR M

        Decrement the content memory, which is specified in  HL register pair

17.INX RP                                          E.g. INX B

        Increment the content of register pair

18. DCX RP                                        E.g. DC B

         Decrement the content of register pair

19. DAD Rp                                        E.g. DAD B

          Add content of register pair to content of HL  register pair & result stored in HL

Logical instructions

1.ANA R                                             E.g. ANA B

          Logically AND the content of register with content   of A

2. ANI 8-bit                                        E.g. ANI 74H

      Logically AND 8-bit data with content of A

3. ANA M                                           E.g. ANA M

         Logically AND content of memory with content of A.  Memory location specified in HL register pair     

4. ORA R                                            E.g. ORA B

          Logically OR the content of register with content   of A

5. ORI 8-bit                                        E.g. ORI 74H

        Logically OR 8-bit data with content of A

6. ORA M                                           E.g. ORA M

         Logically OR content of memory with content of   A. Memory location specified in HL register pair     

7. XRA R                                            E.g. XRA B

          Exclusive-OR the content of register with content    of A

8. XRI 8-bit                                        E.g. XRI 74H

          Exclusive-OR 8-bit data with content of A

9. XRA M                                           E.g. XRA M

         Exclusive-OR content of memory with content of    A. Memory location specified in

         HL register pair

10.CMP R                                           E.g. CMP B

       Compare the content of register with the content of A

11. CPI 8-bit                                       E.g. CPI 34H

        Compare the 8-bit data with the content of A

Branch Instructions

1.JMP 16-bit address                          E.g. JMP 2050H

           Change program sequence to the specified memory

2. JZ 16-bit address                            E.g. JZ 2050H

          Change program sequence to specified memory  location, If the zero flag is set.

3. JNZ 16-bit address                         E.g. JNZ 2050H

          Change program sequence to specified memory  location, If the zero flag is reset.

4.JC 16-bit address                             E.g. JZ 2050H

        Change program sequence to specified memory   location, If the carry flag is set.

5. JNC 16-bit address                         E.g. JNC 2050H

          Change program sequence to specified memory   location, If the carry flag is reset.

6.CALL 16-bit address                       E.g. CALL 2040H

     Change the program sequence to the location of    subroutine.

7. RET                                                 E.g. RET

       Returning to the main program after completing subroutine program

Machine Control Instructions

1.HLT            

         Stop processing and wait

2. NOP

         Do not perform any operation