Q. Write an 8085 program and draw a flowchart to Transfer block of N-bytes in reverse order from source to destination.(8085 Microprocessor Program)
Flowchart/Algorithm
Program
| Address | Mnemonics | Operand | Opcode | Comments |
| 2000 | MVI | C, 05H | 0E | Initialize reg. C to 05H, i.e. number of bytes. |
| 2001 | 05 | |||
| 2002 | LXI | H, 3000H | 21 | Initialize H-L pair to source memory location. |
| 2003 | 00 | |||
| 2004 | 30 | |||
| 2005 | LXI | D, 3504H | 11 | Initialize D-E pair to destination memory location. |
| 2006 | 04 | |||
| 2007 | 35 | |||
| 2008 | MOV | A, M | 7E | Move the byte from source to accumulator. |
| 2009 | STAX | D | 12 | Store the byte from the accumulator to the destination. |
| 200A | INX | H | 23 | Increment the source pointer H-L pair. |
| 200B | DCX | D | 1B | Decrement the destination pointer D-E pair. |
| 200C | DCR | C | 0D | Decrement counter C. |
| 200D | JNZ | 2008H | C2 | Jump to address 2008H if the counter is not zero. |
| 200E | 08 | |||
| 200F | 20 | |||
| 2010 | HLT | 76 | Halt |
Output
Before Execution:
3000H: 05H
3001H: 02H
3002H: 04H
3003H: 03H
3004H: 02H
After Execution:
3500H: 02H
3501H: 03H
3502H: 04H
3503H: 02H
3504H: 05H
Program Explanation
- This program transfers a block of N-bytes in reverse order from source to destination. The source bytes start from memory location 3000H and needs to be transferred to memory locations 3504H in reverse order.
- In order to transfer these bytes, first, the counter must be initialized to the number of bytes to transfer.
- Then, H-L pair is initialized to point to the source memory location and D-E pair is initialized to point to destination memory location.
- The first byte is moved from source to accumulator and then from there to destination.
- The H-L pair is incremented and D-E pair is decremented to point to the next respective memory locations.
- The counter is decremented and checked whether it has become zero.
- If it hasn’t become zero, it means that there are bytes remaining to be transferred. In this case, the control jumps back to move the next byte from source to destination.
- This process continues until counter becomes zero, i.e. all the bytes have been transferred.
