Exchange of blocks in Z-80

In this section we will see how we can use the Zilog Z-80 Microprocessor to Exchange the contents of each element from two different blocks.

The number of items in each block are given at location 5000H, and the blocks are at position 5050H and 5070H.

So before swapping the items in the memory is looking like this

Address	Value
5000H	04H
	. . .
5050H	89H
5051H	7AH
5052H	2FH
5053H	56H
	. . .
5070H	AFH
5071H	A9H
5072H	FBH
5073H	21H
	. . .

Now, we are writing a program at location 8000H to exchange the block contents.

Program

Address	Hex Codes	Labels	Mnemonics	Comments
8000	21 00 50		LD HL, 5000H	Load the HL pair with 5000H
8003	DD 21 50 50		LD IX, 5050H	Set the index register with 5050H
8007	DD 7E 00		LD A, (IX+00H)	Load Acc with IX + 00H
800A	DD 46 20		LD B, (IX+20H)	Load B with IX + 20H
800D	DD 70 00	LOOP	LD (IX+00H), B	Load B register content at IX + 00H
8010	DD 77 20		LD (IX+20H), A	Load Acc content at IX + 20H
8013	DD 23		INC IX	Increase the IX register
8015	35		DEC (HL)	Decrease the memory content, pointer by HL pair
8016	C2 07 80		JP NZ, LOOP	Jump to Loop, when zero flag is off
8019	76		HALT	Stop the program

Output

Address	Value
5000H	04H
	. . .
5050H	AFH
5051H	A9H
5052H	FBH
5053H	21H
	. . .
5070H	89H
5071H	7AH
5072H	2FH
5073H	56H
	. . .