Familiarization with 8086 microprocessors and experimental kits.

Experiment No. : – 01

Aim of the experiment: –

Familiarization with 8086 microprocessors and experimental kits.

Apparatus required: –

Sl. No.	Name	Specification	Quantity
1	Microprocessor kit	8086 microprocessor	1 no.
2	Keyboard		1 no.

Diagram: –

Theory: –

Introduction of 8086 Microprocessor- A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit (IC) or a small number of ICs. The micro- processor contains the arithmetic, logic, and control circuit by required to perform the functions of a computer’s central processing unit (CPU).

The 8086 Microprocessor is an enhanced version of the 8085 Microprocessor that was designed by Intel in 1976. It is a 16-bit Microprocessor having 20-bit address line and 16-bit data lines that provides up to 1 MB Storage. It is a HMOS microprocessor where the HMOS is used for High-Speed Metal Oxide Semiconductor.

Intel 8086 is built on a single semiconductor chip and packaged in a 40 pin IC Package. The type of package is DIP (Dual inline package).

8086 is designed to operate in two modes i.e, minimum and maximum mode.

The clock speed of this microprocessor varies between 5 MHz, 8 MHz and 10 MHz for different versions.

It supports memory segmentation.

It contains more number of transistors compare to 8085 microprocessor. It contains about 29000 in size.

FEATURES of 8086 MICROPROCESSOR

 (i ) 16 bit processor

  (ii) 20 bit address line

  (iii) 16 bit data line

  (iv) 16 bit ALU

  (v) 16 bit internal data bus

  (vi) 16 bit external data bus

 (vii) (5MHz – 10 MHz)frequency of operation

  (viii) 6 bytes instruction queue

  (ix) 256 Vector interrupt

  (x) Two stages of pipelining (Fetch stage and Execute stage)

   (xi) 1 MB storage access

ARCHITECTURE of 8086 MICROPROCESSOR

ALU(Arithmetic and Logic unit): – It  handles  arithmetic and logic operations.

EU(Execution Unit):-

Its function is to control operations on data using the instruction decoder & ALU.

Fetches instruction codes, stores fetched instruction codes in-first-in-first out register set called a queue.

Reads data from memory and I/O devices.

Write data to memory and I/O devices.

It relocates addresses of operands since it gets un-relocated operand addresses from EU. The EU tells the BIU from where to fetch Instructions or where to read data.

It has following functional parts-
Instruction Queue – When EU executes instructions, the BIU gets 6 bytes of the next instruction and stores them in the Instruction queue and this process is known as instruction pre-fetch. This process increases the speed of the processor.

Segment Registers – Contains addresses of instructions and data in memory which are used by the processor to access memory locations. It points to the starting address of memory segment currently being used.

There are 4 segment registers in 8086-

CS (Code segment Register):- Code segment of the memory holds instruction codes of a program.

DS (Data Segment register) :- The data, variables and constants given in the program are held in the data segment of memory.

SS (stack segment register) :- Stack segment holds addresses and data of subroutines. It also holds the contents of registers and memory Locations given in PUSH instruction.

ES (Extra segment Register) :- Extra segment holds the destination addresses of some data of certain string instructions.

Execution Unit (EU) – Its function is to control operations on data using the instruction decoder & ALU.

The BIU and EU operate in parallel independently. This make processing faster.

General purpose registers, stack pointer, base pointer and Index registers, flag registers (FLAGS), instruction decoder and timing and control unit constitute execution unit.

General Purpose Registers: There are 8 general purpose registers, i.e., AH, AL, BH, BL, CH, CL, DH, and DL. In pairs is referred to the AX, BX, CX, and DX respectively.

Index Register – Stack pointer (SP)

Source Index (ST)

Base pointer (BP)

Destination Index (DI).

Flag Registers:-  It is a 16 bit register that behaves like a flip-flop and changes its status as  per result stored in an accumulator. It has 9 flags and they are divided into two groups: conditional flag and control flag.

Conditional Flags: Carry flag, Auxiliary flag, Parity flag, Zero flag,  Sign   flag, Overflow flag.

Control Flags: Trap flag, interrupt flag, Direction flag.

Stack pointer:- It is a 16 bit register, which holds the address from the start of the segment to the memory location, where a word was most recently stored on the stack.

Address/data bus:- AD0-AD15. These are 16 address/data bus. AD0-AD7 carries low order byte data and AD8-AD15 carries higher order byte data. A16-A19 is address bus.

Power supply:- It uses 5V DC supply at V_CC pin 40, and uses ground at V_SS pin 1 and 20 for its operation.

TYPES of INSTRUCTIONS

The 8086 microprocessor supports 8 types of instructions −

1. Data Transfer Instructions.
2.   Arithmetic Instructions
3.   Bit Manipulation Instructions
4.   String Instructions
5.   Program Execution Transfer Instructions (Branch & Loop   Instructions)
6.   Processor Control Instructions
7.   Iteration Control Instructions

  8. Interrupt Instructions.

1.       Data Transfer Instructions

These instructions are used to transfer the data from the source operand to the destination operand. Following are the list of instructions under this group −

Instruction to transfer a word

MOV − Used to copy the byte or word from the provided source to the provided destination.

PUSH − Used to put a word at the top of the stack.

POP − Used to get a word from the top of the stack to the provided location.

PUSHA − Used to put all the registers into the stack.

POPA − Used to get words from the stack to all registers.

XCHG − Used to exchange the data from two locations.

XLAT − Used to translate a byte in AL using a table in the memory.

Instructions for input and output port transfer

IN − Used to read a byte or word from the provided port to the accumulator.

OUT − Used to send out a byte or word from the accumulator to the provided port.

Instructions to transfer the address

LEA − Used to load the address of operand into the provided register.

LDS − Used to load DS register and other provided register from the memory

LES − Used to load ES register and other provided register from the memory.

Instructions to transfer flag registers

LAHF − Used to load AH with the low byte of the flag register.

SAHF − Used to store AH register to low byte of the flag register.

PUSHF − Used to copy the flag register at the top of the stack.

POPF − Used to copy a word at the top of the stack to the flag register.

2. Arithmetic Instructions

These instructions are used to perform arithmetic operations like addition, subtraction, multiplication, division, etc.

Following is the list of instructions under this group −

Instructions to perform addition

ADD − Used to add the provided byte to byte/word to word.

ADC − Used to add with carry.

INC − Used to increment the provided byte/word by 1.

AAA − Used to adjust ASCII after addition.

DAA − Used to adjust the decimal after the addition/subtraction operation.

Instructions to perform subtraction

SUB − Used to subtract the byte from byte/word from word.

SBB − Used to perform subtraction with borrow.

DEC − Used to decrement the provided byte/word by 1.

NPG − Used to negate each bit of the provided byte/word and add 1/2’s complement.

CMP − Used to compare 2 provided byte/word.

AAS − Used to adjust ASCII codes after subtraction.

DAS − Used to adjust decimal after subtraction.

Instruction to perform multiplication

MUL − Used to multiply unsigned byte by byte/word by word.

IMUL − Used to multiply signed byte by byte/word by word.

AAM − Used to adjust ASCII codes after multiplication.

Instructions to perform division

DIV − Used to divide the unsigned word by byte or unsigned double word by word.

IDIV − Used to divide the signed word by byte or signed double word by word.

AAD − Used to adjust ASCII codes after division.

CBW − Used to fill the upper byte of the word with the copies of the sign bit of the lower byte.

CWD − Used to fill the upper word of the double word with the sign bit of the lower word.

3. Bit Manipulation Instructions

These instructions are used to perform operations where data bits are involved, i.e. operations like logical, shift, etc.

Following is the list of instructions under this group −

Instructions to perform logical operation

NOT − Used to invert each bit of a byte or word.

AND − Used for adding each bit in a byte/word with the corresponding bit in another byte/word.

OR − Used to multiply each bit in a byte/word with the corresponding bit in another byte/word.

XOR − Used to perform Exclusive-OR operation over each bit in a byte/word with the corresponding bit in another byte/word.

TEST − Used to add operands to update flags, without affecting operands.

Instructions to perform shift operations

SHL/SAL − Used to shift bits of a byte/word towards left and put zero(S) in LSBs.

SHR − Used to shift bits of a byte/word towards the right and put zero(S) in MSBs.

SAR − Used to shift bits of a byte/word towards the right and copy the old MSB into the new MSB.

Instructions to perform rotate operations

ROL − Used to rotate bits of byte/word towards the left, i.e. MSB to LSB and to Carry Flag [CF].

ROR − Used to rotate bits of byte/word towards the right, i.e. LSB to MSB and to Carry Flag [CF].

RCR − Used to rotate bits of byte/word towards the right, i.e. LSB to CF and CF to MSB.

RCL − Used to rotate bits of byte/word towards the left, i.e. MSB to CF and CF to LSB.

4. String Instructions

String is a group of bytes/words and their memory is always allocated in a sequential order.

Following is the list of instructions under this group −

REP − Used to repeat the given instruction till CX ≠ 0.

REPE/REPZ − Used to repeat the given instruction until CX = 0 or zero flag ZF = 1.

REPNE/REPNZ − Used to repeat the given instruction until CX = 0 or zero flag ZF = 1.

MOVS/MOVSB/MOVSW − Used to move the byte/word from one string to another.

COMS/COMPSB/COMPSW − Used to compare two string bytes/words.

INS/INSB/INSW − Used as an input string/byte/word from the I/O port to the provided memory location.

OUTS/OUTSB/OUTSW − Used as an output string/byte/word from the provided memory location to the I/O port.

SCAS/SCASB/SCASW − Used to scan a string and compare its byte with a byte in AL or string word with a word in AX.

LODS/LODSB/LODSW − Used to store the string byte into AL or string word into AX.

5. Program Execution Transfer Instructions (Branch and Loop Instructions)

CALL − Used to call a procedure and save their return address to the stack.

RET − Used to return from the procedure to the main program.

JMP − Used to jump to the provided address to proceed to the next instruction.

Instructions to transfer the instruction during an execution with some conditions −

JA/JNBE − Used to jump if above/not below/equal instruction satisfies.

JAE/JNB − Used to jump if the above/not below instruction satisfies.

JBE/JNA − Used to jump if below/equal/ not above instruction satisfies.

JC − Used to jump if carry flag CF = 1

JE/JZ − Used to jump if equal/zero flag ZF = 1

JG/JNLE − Used to jump if greater/not less than/equal instruction satisfies.

JGE/JNL − Used to jump if greater than/equal/not less than instruction satisfies.

JL/JNGE − Used to jump if less than/not greater than/equal instruction satisfies.

JLE/JNG − Used to jump if less than/equal/if not greater than instruction satisfies.

JNC − Used to jump if no carry flag (CF = 0)

JNE/JNZ − Used to jump if not equal/zero flag ZF = 0

JNO − Used to jump if no overflow flag OF = 0

JNP/JPO − Used to jump if not parity/parity odd PF = 0

JNS − Used to jump if not sign SF = 0

JO − Used to jump if overflow flag OF = 1

JP/JPE − Used to jump if parity/parity even PF = 1

JS − Used to jump if sign flag SF = 1

6. Processor Control Instructions

These instructions are used to control the processor action by setting/resetting the flag values.

Following are the instructions under this group −

STC − Used to set carry flag CF to 1

CLC − Used to clear/reset carry flag CF to 0

CMC − Used to put complement at the state of carry flag CF.

STD − Used to set the direction flag DF to 1

CLD − Used to clear/reset the direction flag DF to 0

STI − Used to set the interrupt enable flag to 1, i.e., enable INTR input.

CLI − Used to clear the interrupt enable flag to 0, i.e., disable INTR input.

7. Iteration Control Instructions

These instructions are used to execute the given instructions for number of times.

Following is the list of instructions under this group −

LOOP − Used to loop a group of instructions until the condition satisfies, i.e., CX = 0

LOOPE/LOOPZ − Used to loop a group of instructions till it satisfies ZF = 1 & CX = 0

LOOPNE/LOOPNZ − Used to loop a group of instructions till it satisfies ZF = 0 & CX = 0

JCXZ − Used to jump to the provided address if CX = 0

8. Interrupt Instructions

These instructions are used to call the interrupt during program execution.

INT − Used to interrupt the program during execution and calling service specified.

INTO − Used to interrupt the program during execution if OF = 1

IRET − Used to return from interrupt service to the main program

ADDRESSING MODES

The different ways in which a source operand is denoted in an instruction is known as addressing modes. There are 8 different addressing modes in 8086 programming −

1. Immediate addressing mode

MOV CX, 4929 H

 ADD AX, 2387 H

 MOV AL, FFH

2. Register addressing mode

MOV CX, AX

ADD BX, AX

3. Direct addressing mode

MOV AX, [1592H]

MOV AL, [0300H]

4. Register indirect addressing mode

MOV AX, [BX] ; Suppose the register BX contains 4895H, then the contents

                ; 4895H are moved to AX

ADD CX, [BX]

5. Based addressing mode

MOV DX, [BX+04]

 ADD CL, [BX+08]

6. Indexed addressing mode

MOV BX, [SI+16]

 ADD AL, [DI+16]

7. Based-index addressing mode

ADD CX, [AX+SI]

 MOV AX, [AX+DI]

8. Based indexed with displacement mode

MOV AX, [BX+DI+08]

 ADD CX, [BX+SI+16]

Procedures: –

1. Press “E” :—> Expand.
2. Press “Enter”:—>ASM/DSM.
3. Press “A” for Assembler.
4. 1000:0100: MOV AX, 1234
5. 1000:0103: MOV BX, 5678
6. 1000:0106: ADD AX,BX
7. 1000:0108: INT A5
8. 1000:010A:
9. Press “Enter”.
10. Press “Q” for Exit.
11. COMMAND: (Goes to command mode).
12. Press “G” for Execution of Program.
13. Press “Enter” : Brust.
14. Press “Enter” : SRC_ SEGM.
15. Enter “1000”: Segment address.
16. Give Offset address “0100”.
17. Press “Enter”.
18. Wait.
19. Command: (Goes to Command mode)
20. Press “S” for checking contains of register.
21. Substut ?
22. Press “Enter”.
23. Memory: then press any key two times.
24. IO Register.
25. Press” Enter”.
26. Name:
27. Press “Enter” : AX: 68AC (Result i.e 1234+5678)
28. Again Press “Enter”: BX: 5678.

Procedures to operate kit using Dissembler

1. Press “E”: for Expand.
2. Press “Enter”:—>ASM/DSM.
3. Press “U” for Dissembler.
4. Press “F9 or F10”
5. Press “Enter”. then:
6. 1000:0100 B8 1234 MOV AX, 1234
7. 1000:0103 B9 5678 MOV BX, 5678
8. 1000:0106 01 D8 ADD AX, BX
9. 1000:0108 CD A5 INT A5
10. 1000: 010A 90 NOP
11. Press “Q” for Exit.
12. Press “Enter”.