8085 program to swap two 16 bit numbers using Direct addressing mode

Problem – Write a program to swap two 16-bit numbers using direct addressing mode where starting address is 2000 and the first 16-bit number is stored at 3000 and the second 16-bit number is stored at 3002 memory address.

Example –

Algorithm –

1. Load a 16-bit number from memory 3000 into a register pair (H-L)
2. Exchange the register pairs
3. Load a 16-bit number from memory 3002 into a register pair (H-L)
4. Exchange both the register pairs
5. Stop

Program –

Memory	Mnemonics	Operands	Comment
2000	LHLD	[3000]	[H-L] <- [3000]
2003	XCHG		[H-L] [D-E]
2004	LHLD	[3002]	[H-L] <- [3002]
2007	XCHG		[H-L] [D-E]
2008	HLT		Stop

Explanation – Registers (H-L) pair, (D-E) pair are used for general purpose.

1. LHLD is used to load register pair H-L direct using 16-bit address (3 Byte instruction)
2. XCHG is used to exchange the data of both the register pair (H-L), (D-E) (1 Byte instruction)
3. HLT is used to halt the program.