Programs of microprocessor
Microprocessor cannot understand a program written in Assembly Language .
Instruction are divided into bit pattern of word in byte as op-code(operation code) and operation.
Instruction format has three types
1.One byte-has op-code
2.Two byte- has op-code and address
3.Three byte -has code and address lower byte and address higher byte
1 byte
2 byte
| opcode |
| Data / address Lower byte |
| Data Address Higher byte |
3 byte
Instructions set for 8085 are classified into five categories:
1.Data transfer group instructions
2.Arithmetic group of instructions
3.Logical group
4.Branching group
5.Machine Level
A program known in Assembler is used to covert a Assembly language program to machine language.
I) Data transfer copy operation:-
1)Load a 8 bit number in a register
2)Copy from Register to Register
3)Copy between Register and Memory
4)Copy between Input/Output Port and Accumulator
5)Load a 16 bit number in a Register pair
6) Copy between Register pair and Stack memory
Example :-
1.Load a 8 bit number 4F in register B -MVI B ,4FH
2.Copy from Register B to Register A -MOV A,B
3.Load a 16 bit number 2050 in Register pair HL -LXI H,2050H
4.Copy from Register B to Memory Address 2050 - MOV M,B
5.Copy between Input/Output Port and Accumulator- OUT 01H IN 07H
2)Arithmetic operations and instructions
1.Add 8 bit number 32 H to Accumulator -ADI 32 H
2.Add contents of Register B to Accumulator - ADD B
3.Subtract a 8 bit number 32 H from Accumulator - SUI 32H
4.Subtract contents of Register C from Accumulator -SUB C
5.Increment the contents of Register D by 1 - INR D
6.Decrement the contents of Register E by 1 - DCR E
3)Logical and Bit Manipulation operations and instructions
1.Logically AND Register H with Accumulator -ANA H
2.Logically OR Register L with Accumulator -ORA L
3.Logically XOR Register B with Accumulator - XRA B
4.Compare contents of Register C with Accumulator -CMP C
5.Complement Accumulator -CMA
6.Rotate Accumulator Left -RAL
Program to add two 8 bit numbers and store result in register C
1.Get two numbers
a) Load first no. in register D MVI D , 2H
b)Load second no. in register E MVI E , 3H
2.Add them
a) Copy register D to A MOV A , D
b) Add register E to A ADD E
3. Store result
a)Copy A to register C MOV C , A
4.Stop
a)Stop processing HLT
Program to add 8 bit number result can be more than 8 bits i.e.with carry present
1.Get two numbers
a) Load first no. in register D MVI D , 2H
b)Load second no. in register E MVI E , 3H
2.Add them
a) Copy register D to A MOV A , D
b) Add register E to A ADD E
3. Store result
a)Copy A to register C MOV C , A
4.Carry
a)Use conditional Jump instructions JNC END
5.Change
a)Clear register B MVI B ,0H
b)Increment B INR B
6.Stop
a)Stop processing HLT
