Familiarization with 8086 microprocessors and experimental kits.

Experiment No. : – 01

Aim of the experiment: –

Apparatus required: –

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

table No. 1.1

Diagram: –

Theory: –

A microprocessor is a controlling unit of a micro-computer, fabricated on a small chip capable of performing Arithmetic Logical Unit (ALU) operations and communicating with the other devices connected to it.

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 address lines and16 data lines that provides up to 1MB storage.

FEATURES of 8086 MICROPROCESSOR

a. 16 bit processor

b. 20 bit address line

c. 16 bit data line

d. 16 bit ALU

e. 16 bit internal data bus

f. 16 bit external data bus

g. (5MHz – 10 MHz)frequency of operation

h. 6 bytes instruction queue

i. 256 Vector interrupt

j. Two stages of pipelining (Fetch stage and Execute stage)

k. 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

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.

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.

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.

BIU (Bus Interface Unit):-BIU takes care of all data and addresses transfers on the buses for the EU. It has the following functional parts −

Instruction queue : 6 BYTES

Segment register :- Code Segment (CS), Data Segment (DS), Stack Segment (SS) & Extra Segment (ES).

Instruction pointer:- It is a 16-bit register used to hold the address of the next instruction to be executed.

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 −

Data Transfer Instructions.
Arithmetic Instructions
Bit Manipulation Instructions
String Instructions
Program Execution Transfer Instructions (Branch & Loop Instructions)
Processor Control Instructions
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 −

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. ET-8086LCD – (by Excel Technologies).

Microsoft’s MASM software is a utility program for Assembling the 8086 Assembly codes into 8086 machine codes. The utility was actually meant for debugging the programs of 8086 / 8088 based Personal computers on the computer and editing and running them using the Debug Command of the Personal computer DOS system

However with some help from other utilities available, the same can be used to compile the 8086 Assembly language programs and generate the Hex File which then can be used by other equipment compatible with the Intel Hex file system.

Step 1. Download the DOSBox setup and MASM folder from the google drive link provided to you . https://drive.google.com/drive/folders/1NZ3JMnN0kdpubbs53EGQ9-He9Rh8ZMcT

Step 2. Install DOSBox on your computer

Step 3. Copy the MASM folder to the C drive of your Computer .

Step 4. Create an ASM File using an Editor of Window

The Syntax etc. for the various commands will become clear when we use these with some Example: – An example of Addition with File name ADDNEW.ASM is available in the Folder. You can write your own program also.

Please note that the The commands in the beginning like

CODE SEGMENT PUBLIC

ASSUME CS:CODE,DS:CODE,ES:CODE

And the commands in the end like

CODE ENDS

END STRT

Are a must and must be entered

Step 5. Open DOSBox and type “ mount c: c:\MASM” the Press Enter . Type “ c:” then Press Enter.

Step 6. To Edit and Existing file Type “ EDIT ADDNEW.ASM” then press Enter.

( A Blue Windows open up with the new file name written on top of the windows ). Type the program as given below and then save the same using

Make the Changes to the program if required and save the file from the File Menu.

Step 7. Creating a Obj file using MASM

Now let us create an OBJ file from the ASM File

MASM ADDNEW.ASM <Enter>

The system will ask for the file extensions etc. just press Enter every time, the system will generate an OBJ file and give a message to that effect.

If there are errors in the Assembly programs, the system will give error and give the line numbers along with it. Go back to the ASM file using the EDIT command. Make the necessary corrections and then Assemble again using the MASM command.

Step 8. Creating an EXE File from the OBJ File using the following command

LINK ADDNEW.OBJ <Enter> and then keep pressing Enter when prompted to answer a query.

The system will generate and EXE file named ADDNEW.EXE

Step 9. Creating a BIN File from the EXE File using the following Command

EXE2BIN ADDNEW.EXE ADDNEW.BIN <Enter>

Press Enter when prompted to an inquiry and the system will generate a BIN File

Step 10. Use the Utility BIN2HEX to generate the required Hex file as given below

BIN2HEX ADDNEW.BIN ADDNEW.HEX <Enter>

The system will successfully generate a Hex File which now can be down loaded in the Kit using the Downloading command given in the manual of the 8086LCD Kit.