MICROPROCESSORS & APPLICATIONS LAB MANUAL (first half set))

 1. INTRODUCTION TO 8085

INTEL 8085 is one of the most popular 8-bit microprocessor capable of addressing 64 KB of memory and its architecture is simple. The device has 40 pins, requires +5 V power supply and can operate with 3MHz single phase clock.

ALU (Arithmetic Logic Unit):

The 8085A has a simple 8-bit ALU and it works in coordination with the accumulator, temporary registers, 5 flags and arithmetic and logic circuits. ALU has the capability of performing several mathematical and logical operations. The temporary registers are used to hold the data during an arithmetic and logic operation. The result is stored in the accumulator and the flags are set or reset according to the result of the operation. The flags are affected by the arithmetic and logic operation. They are as follows:

·         Sign flag

After the execution of the arithmetic - logic operation if the bit D7 of the result is 1, the sign flag is set. This flag is used with signed numbers. If it is 1, it is a negative number and if it is 0, it is a positive number.

·         Zero flag

The zero flag is set if the ALU operation results in zero. This flag is modified by the result in the accumulator as well as in other registers.

·         Auxillary carry flag

In an arithmetic operation when a carry is generated by digit D3 and passed on to D4, the auxillary flag is set.

·         Parity flag

After arithmetic – logic operation, if the result has an even number of 1’s the flag is set. If it has odd number of 1’s it is reset.

·         Carry flag

If an arithmetic operation results in a carry, the carry flag is set. The carry flag also serves as a borrow flag for subtraction.

Timing and control unit

      This unit synchronizes all the microprocessor operation with a clock and generates the control signals necessary for communication between the microprocessor and peripherals. The control signals RD (read) and WR (write) indicate the availability of data on the data bus.

Instruction register and decoder

      The instruction register and decoder are part of the ALU. When an instruction is fetched from memory it is loaded in the instruction register. The decoder decodes the instruction and establishes the sequence of events to follow.

Register array

      The 8085 has six general purpose registers to store 8-bit data during program execution. These registers are identified as B, C, D, E, H and L. they can be combined as BC, DE and HL to perform 16-bit operation.

Accumulator

      Accumulator is an 8-bit register that is part of the ALU. This register is used to store 8-bit data and to perform arithmetic and logic operation. The result of an operation is stored in the accumulator.

Program counter

The program counter is a 16-bit register used to point to the memory address of the next instruction to be executed.

Stack pointer

It is a 16-bit register which points to the memory location in R/W memory, called the Stack.

Communication lines

8085 microprocessor performs data transfer operations using three communication lines called buses. They are address bus, data bus and control bus.

·         Address bus – it is a group of 16-bit lines generally identified as A₀ – A_15.  The address bus is unidirectional i.e., the bits flow in one direction from microprocessor to the peripheral devices. It is capable of addressing 2¹⁶ memory locations.

·         Data bus – it is a group of 8 lines used for data flow and it is bidirectional. The data ranges from 00 – FF.

·         Control bus – it consist of various single lines that carry synchronizing signals. The microprocessor uses such signals for timing purpose.

 

2(A). 8 BIT DATA ADDITION

AIM:

             To add two 8 bit numbers stored at consecutive memory locations.

ALGORITHM:

1.      Initialize memory pointer to data location.

2.      Get the first number from memory in accumulator.

3.      Get the second number and add it to the accumulator.

4.      Store the answer at another memory location.

RESULT:

Thus the 8 bit numbers stored at 4500 &4501 are added and the result stored at 4502 & 4503.

PROGRAM:

ADDRESS	OPCODE	LABEL	MNEMONICS	OPERAND	COMMENT
4100		START	MVI	C, 00	Clear C reg.
4101
4102			LXI	H, 4500	Initialize HL reg. to 4500
4103
4104
4105			MOV	A, M	Transfer first data to accumulator
4106			INX	H	Increment HL reg.  to point next memory    Location.
4107			ADD	M	Add first number to acc. Content.
4108			JNC	L1	Jump to location if result does not yield carry.
4109
410A
410B			INR	C	Increment C reg.
410C		L1	INX	H	Increment HL reg.  to point next memory Location.
410D			MOV	M, A	Transfer the result from acc. to memory.
410E			INX	H	Increment HL reg. to point next memory Location.
410F			MOV	M, C	Move carry to memory
4110			HLT		Stop the program

OBSERVATION:

INPUT		OUTPUT
4500		4502
4501		4503

                                                             

2(B). 8 BIT DATA SUBTRACTION

AIM:

             To Subtract two 8 bit numbers stored at consecutive memory locations.

ALGORITHM:

1.      Initialize memory pointer to data location.

2.      Get the first number from memory in accumulator.

3.      Get the second number and subtract from the accumulator.

4.      If the result yields a borrow, the content of the acc. is complemented and 01H is added to it (2’s complement). A register is cleared and the content of that reg. is incremented in case there is a borrow. If there is no borrow the content of the acc. is directly taken as the result.

5.      Store the answer at next memory location.

RESULT:

Thus the 8 bit numbers stored at 4500 &4501 are subtracted and the result stored at 4502 & 4503.

PROGRAM:

ADDRESS	OPCODE	LABEL	MNEMONICS	OPERAND	COMMENT
4100		START	MVI	C, 00	Clear C reg.
4101
4102			LXI	H, 4500	Initialize HL reg. to 4500
4103
4104
4105			MOV	A, M	Transfer first data to accumulator
4106			INX	H	Increment HL reg. to point next mem. Location.
4107			SUB	M	Subtract first number from acc. Content.
4108			JNC	L1	Jump to location if result does not yield borrow.
4109
410A
410B			INR	C	Increment C reg.
410C			CMA		Complement the Acc. content
410D			ADI	01H	Add 01H to content of  acc.
410E
410F		L1	INX	H	Increment HL reg. to point next mem. Location.
4110			MOV	M, A	Transfer the result from acc. to memory.
4111			INX	H	Increment HL reg. to point next mem. Location.
4112			MOV	M, C	Move carry to mem.
4113			HLT		Stop the program

OBSERVATION:

INPUT		OUTPUT
4500		4502
4501		4503

 

3(A).  8 BIT DATA MULTIPLICATION

AIM:

             To multiply two 8 bit numbers stored at consecutive memory locations and store the result in memory.

ALGORITHM:

LOGIC: Multiplication can be done by repeated addition.

1.      Initialize memory pointer to data location.

2.      Move multiplicand to a register.

3.      Move the multiplier to another register.

4.      Clear the accumulator.

5.      Add multiplicand to accumulator

6.      Decrement multiplier

7.      Repeat step 5 till multiplier comes to zero.

8.      The result, which is in the accumulator, is stored in a memory location.

RESULT:

Thus the 8-bit multiplication was done in 8085mp using repeated addition method.

PROGRAM:

ADDRESS	OPCODE	LABEL	MNEMONICS	OPERAND	COMMENT
4100		START	LXI	H, 4500	Initialize HL reg. to 4500 Transfer first data to reg. B
4101
4102
4103			MOV	B, M
4104			INX	H	Increment HL reg.  to point next mem. Location.
4105			MVI	A, 00H	Clear the acc.
4106
4107			MVI	C, 00H	Clear C reg for carry
4108
4109		L1	ADD	M	Add multiplicand  multiplier times.
410A			JNC	NEXT	Jump to NEXT if there is no carry
410B
410C
410D			INR	C	Increment C reg
410E		NEXT	DCR	B	Decrement B reg
410F			JNZ	L1	Jump to L1 if B is not zero.
4110
4111
4112			INX	H	Increment HL reg. to point next mem. Location.
4113			MOV	M, A	Transfer the result from acc. to memory.
4114			INX	H	Increment HL reg. to point next mem. Location.
4115			MOV	M, C	Transfer the result from C reg. to memory.
4116			HLT		Stop the program

OBSERVATION:

INPUT		OUTPUT
4500		4502
4501		4503

3(B). 8 BIT DIVISION

AIM:

            To divide two 8-bit numbers and store the result in memory.

ALGORITHM:

LOGIC: Division is done using the method Repeated subtraction.

1.      Load Divisor and Dividend

2.      Subtract divisor from dividend

3.      Count the number of times of subtraction which equals the quotient

4.      Stop subtraction when the dividend is less than the divisor .The dividend now becomes the remainder. Otherwise go to step 2.

5.      stop the program execution.

RESULT:

            Thus an ALP was written for 8-bit division using repeated subtraction method and executed using 8085m p kits

PROGRAM:

ADDRESS	OPCODE	LABEL	MNEMONICS	OPERAND	COMMENTS
4100			MVI	B,00	Clear B reg for quotient
4101
4102			LXI	H,4500	Initialize HL reg. to 4500H
4103
4104
4105			MOV	A,M	Transfer dividend to acc.
4106			INX	H	Increment HL reg.  to point next mem. Location.
4107		LOOP	SUB	M	Subtract divisor from dividend
4108			INR	B	Increment B reg
4109			JNC	LOOP	Jump to LOOP  if result does not yield borrow
410A
410B
410C			ADD	M	Add divisor to acc.
410D			DCR	B	Decrement B reg
410E			INX	H	Increment HL reg. to point next mem. Location.
410F			MOV	M,A	Transfer the remainder from acc. to memory.
4110			INX	H	Increment HL reg. to point next mem. Location.
4111			MOV	M,B	Transfer the quotient from B reg. to memory.
4112			HLT		Stop the program

OBSERVATION:

S.NO	INPUT		OUTPUT
	ADDRESS	DATA	ADDRESS	DATA
1	4500		4502
	4501		4503
2	4500		4502
	4501		4503

4(A).  16 BIT DATA ADDITION

AIM:

            To add two 16-bit numbers stored at consecutive memory locations.

ALGORITHM:

1.      Initialize memory pointer to data location.

2.      Get the first number from memory and store in Register pair.

3.      Get the second number in memory and add it to the Register pair.

4.      Store the sum & carry in separate memory locations.

RESULT:

Thus an ALP program for 16-bit addition was written and executed in 8085mp using special instructions.

PROGRAM:

ADDRESS	OPCODE	LABEL	MNEMONICS	OPERAND	COMMENT
8000		START	LHLD	8050H	Load the augend in DE pair through HL pair.
8001
8002
8003			XCHG
8004			LHLD	8052H	Load the addend in HL pair.
8005
8006
8007			MVI	A, 00H	Initialize reg. A for carry
8008
8009			DAD	D	Add the contents of HL Pair with that of DE pair.
800A			JNC	LOOP	If there is no carry, go to the instruction labeled LOOP.
800B
800C
800D			INR	A	Otherwise increment  reg. A
800E		LOOP	SHLD	8054H	Store the content of HL Pair in 8054H(LSB of sum)
800F
8010
8011			STA	8056H	Store the carry in 8056H through Acc. (MSB of sum).
8012
8013
8014			HLT		Stop the program.

OBSERVATION:

INPUT		OUTPUT
ADDRESS	DATA	ADDRESS	DATA
8050H		8054H
8051H		8055H
8052H		8056H
8053H

                                                             

 

4(B). 16 BIT DATA SUBTRACTION

AIM:

             To subtract two 16-bit numbers stored at consecutive memory locations.

ALGORITHM:

1.      Initialize memory pointer to data location.

2.      Get the subtrahend from memory and transfer it to register pair.

3.      Get the minuend from memory and store it in another register pair.

4.      Subtract subtrahend from minuend.

5.      Store the difference and borrow in different memory locations.

RESULT:

Thus an ALP program for subtracting two 16-bit numbers was written and executed.

   

PROGRAM:

ADDRESS	OPCODE	LABEL	MNEMO NICS	OPER AND	COMMENTS
8000		START	MVI	C, 00	Initialize C reg.
8001
8002			LHLD	8050H	Load the subtrahend in DE reg. Pair through HL reg. pair.
8003
8004
8005			XCHG
8006			LHLD	8052H	Load the minuend in HL reg. Pair.
8007
8008
8009			MOV	A, L	Move the content of reg. L to Acc.
800A			SUB	E	Subtract the content of  reg. E from that of acc.
800B			MOV	L, A	Move the content of Acc. to reg. L
800C			MOV	A, H	Move the content of reg. H to Acc.
800D			SBB	D	Subtract content of reg. D with that of Acc.
800E			MOV	H, A	Transfer content of acc. to reg. H
800F			SHLD	8054H	Store the content of HL pair in memory location 8504H.
8010
8011
8012			JNC	NEXT	If there is borrow, go to the instruction labeled NEXT.
8013
8014
8015			INR	C	Increment reg. C
8016		NEXT	MOV	A, C	Transfer the content of reg. C to Acc.
8017			STA	8056H	Store the content of acc. to the memory location 8506H
8018
8019
801A			HLT		Stop the program execution.

OBSERVATION:

INPUT		OUTPUT
ADDRESS	DATA	ADDRESS	DATA
8050H		8054H
8051H		8055H
8052H		8056H
8053H

 

5(A). 16 BIT MULTIPLICATION

AIM:

                To multiply two 16 bit numbers and store the result in memory.

ALGORITHM:

1. Get the multiplier and multiplicand.
2. Initialize a register to store partial product.
3. Add multiplicand, multiplier times.
4. Store the result in consecutive memory locations.

RESULT:

Thus the 16-bit multiplication was done in 8085mp using repeated addition method.

ADDRESS	OPCODE	LABEL	MNEMONICS	OPERAND	COMMENTS
8000		START	LHLD	8050	Load the first No. in stack pointer through HL reg. pair
8001
8002
8003			SPHL
8004			LHLD	8052	Load the second No. in HL reg. pair & Exchange with DE reg. pair.
8005
8006
8007			XCHG
8008			LXI	H, 0000H	Clear HL & DE reg. pairs.
8009
800A
800B			LXI	B, 0000H
800C
800D
800E		LOOP	DAD	SP	Add SP with HL pair.
800F			JNC	NEXT	If there is no carry, go to the instruction labeled NEXT
8010
8011
8012			INX	B	Increment BC reg. pair
8013		NEXT	DCX	D	Decrement DE reg. pair.
8014			MOV	A,E	Move the content of reg. E to Acc.
8015			ORA	D	OR Acc. with D reg.
8016			JNZ	LOOP	If there is no zero, go to instruction labeled LOOP
8017
8018
8019			SHLD	8054	Store the content of HL pair in memory locations 8054 & 8055.
801A
801B
801C			MOV	A, C	Move the content of reg. C to Acc.
801D			STA	8056	Store the content of Acc. in memory location 8056.
801E
801F
8020			MOV	A, B	Move the content of reg. B to Acc.
8021			STA	8057	Store the content of Acc. in memory location 8056.
8022
8023
8024			HLT		Stop  program execution

OBSERVATION:

INPUT		OUTPUT
ADDRESS	DATA	ADDRESS	DATA
8050		8054
8051		8055
8052		8056
8053		8057

5(B). 16- BIT DIVISION

AIM:

             To divide two 16-bit numbers and store the result in memory using 8085 mnemonics.

ALGORITHM:

1. Get the dividend and divisor.
2. Initialize the register for quotient.
3. Repeatedly subtract divisor from dividend till dividend becomes less than divisor.
4. Count the number of subtraction which equals the quotient.
5. Store the result in memory.

RESULT:

Thus the 16-bit Division was done in 8085mp using repeated subtraction method.

 

PROGRAM:

ADDRESS	OPCODE	LABEL	MNEMONICS	OPERA ND	COMMENTS
8000		START	LHLD	8052	Load the first No. in stack pointer through HL reg. pair
8001
8002
8003			XCHG
8004			LHLD	8050	Load the second No. in HL reg. pair & Exchange with DE reg. pair.
8005
8006
8007			LXI	B, 0000H	Clear BC reg. pair.
8008
8009
800A		LOOP	MOV	A, L	Move the content of reg. L to Acc.
800B			SUB	E	Subtract reg. E from that of Acc.
800C			MOV	L, A	Move the content of Acc to  L.
800D			MOV	A, H	Move the content of reg. H Acc.
800E			SBB	D	Subtract  reg. D from that of Acc.
800F			MOV	H, A	Move the content of Acc to  H.
8010			INX	B	Increment reg.  Pair BC
8011			JNC	LOOP	If there is no carry, go to the location labeled LOOP.
8012
8013
8014			DCX	B	Decrement BC reg. pair.
8015			DAD	D	Add content of HL and DE reg. pairs.
8016			SHLD	8054	Store the content of HL pair in 8054 & 8055.
8017
8018
8019			MOV	A, C	Move the content of reg. C to Acc.
801A			STA	8056	Store the content of Acc. in memory 8056
801B
801C
801D			MOV	A, B	Move the content of reg. B to Acc.
801E			STA	8057	Store the content of Acc. in memory 8057.
801F
8020
8021			HLT		Stop the program execution.

OBSERVATION:

INPUT		OUTPUT
ADDRESS	DATA	ADDRESS	DATA
8050		8054
8051		8055
8052		8056
8053		8057