8085 program to move blocks of bits from source location to a destination location

Problem – Write a program to move blocks of bits from source location starting at 2500 to destination location starting from 2600 where size of blocks is 05 bytes. Example – Algorithm –

1. Load register pair H-L with the address 2500H
2. Load register pair D-E with the address 2600H
3. Move the content at memory location into accumulator
4. Store the content of accumulator into memory pointed by D-E
5. Increment value of register pair H-L and D-E by 1
6. Decrements value of register C by 1
7. If zero flag not equal to 1, go to step 3
8. Stop

Program –

Memory	Mnemonics	Operands	Comment
2000	MVI	C, 05	[C] <- 05
2002	LXI	H, 2500	[H-L] <- 2500
2005	LXI	D, 2600	[D-E] <- 2600
2008	MOV	A, M	[A] <- [[H-L]]
2009	STAX	D	[A] -> [[D-E]]
200A	INX	H	[H-L] <- [H-L] + 1
200B	INX	D	[D-E] <- [D-E] + 1
200C	DCR	C	[C] <- [C] – 1
200D	JNZ	2008	Jump if not zero to 2008
2010	HLT		Stop

Explanation – Registers A, D, E, H, L, C are used for general purpose:

1. MOV is used to transfer the data from memory to accumulator (1 Byte)
2. LXI is used to load register pair immediately using 16-bit address (3 Byte instruction)
3. MVI is used to move data immediately into any of registers (2 Byte)
4. STAX is used to store accumulator into register pair indirectly (3 Byte instruction)
5. DCR is used to decrease register by 1 (1 Byte instruction)
6. INX is used to increase register pair by 1 (1 Byte instruction)
7. JNZ is used to jump if not zero to given memory location (3 Byte instruction)
8. HLT is used to halt the program

Advantages:

• The program is simple and easy to understand, making it useful for teaching purposes.
  
• It can be used to efficiently move blocks of data within a memory, such as copying data from one buffer to another, or shifting bits within a data structure.
  
• The program is customizable, as the source and destination addresses, as well as the block size, can be easily changed.

Disadvantages:

• The program is not optimized for speed, as it uses multiple instructions to move each byte of data.
  
• It is not suitable for moving large blocks of data, as it requires a loop that iterates over each byte individually.
  
• The program does not check for errors or boundary conditions, such as when the source or destination address is outside the valid memory range.