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8085 Block movement with overlap
In this program, we will see how to move blocks of data from one place to another.
Problem Statement
Write 8085 Assembly language program to move a data block. The blocks are assumed to be overlapping. The block size is given, the block is starting from Xand we have to move it to the location Y.
Discussion
The overlapping block movement is tricky; we need to use some special tricks to move a block in overlapping address locations. Here the block is starting at position X, we have to move it to position Y. The location Y is inside the block. So Y < X + block size.
In this program, the data are stored at location 8010H, and we will place it 8014H. The block size is stored at location 8000H.
To move a block into some overlapping locations, we will start from the end element of the block. So at first the last element of the block is moved, then the previous bytes are moved.
Input
| Address | Data |
|---|---|
| . . . | . . . |
| 8000 | 07 |
| . . . | . . . |
| 8010 | 11 |
| 8011 | 22 |
| 8012 | 33 |
| 8013 | 44 |
| 8014 | 55 |
| 8015 | 66 |
| 8016 | 77 |
| . . . | . . . |
Flow Diagram
Program
| Address | HEX Codes | Labels | Mnemonics | Comments | |
|---|---|---|---|---|---|
| F000 | 21, 00, 80 | LXI H, 8000H | Load the location to find block size | ||
| F003 | 4E | MOV C, M | store block size into C register | ||
| F004 | 06, 00 | MVI B,00H | clear B register | ||
| F006 | 21,10, 80 | LXI H,8010H | load the source address to HL pair | ||
| F009 | 11, 14, 80 | LXI D, 8014H | load the destination address to DE pair | ||
| F00C | 09 | DAD B | Add BC with HL to point next location of the end of the source block | ||
| F00D | 2B | DCX H | Point last element | ||
| F00E | EB | XCHG | Swap DE and HL pair content | ||
| F00F | 09 | DAD B | Add BC with HL to point next location of the end of dest block | ||
| F010 | 2B | DCX H | Point last element | ||
| F011 | EB | XCH G | Swap DE and HL pair content | ||
| F012 | 7E | LOOP | MOV A, M | Load Acc with the memory element | |
| F013 | 12 | STAX D | Store acc content to the memory pointed by D | ||
| F014 | 1B | DCX D | Decrease DE register pair | ||
| F015 | 2B | DCX H | Decrease HL register pair | ||
| F016 | 0D | DCR C | Decrease C register | ||
| F017 | C2, 12, F0 | JNZ LOOP | Jump to Loop | ||
| F01A | 76 | HLT | Terminate the program | ||
Output:
| Address | Data |
|---|---|
| . . . | . . . |
| 8000 | 07 |
| . . . | . . . |
| 8010 | 11 |
| 8011 | 22 |
| 8012 | 33 |
| 8013 | 44 |
| 8014 | 11 |
| 8015 | 22 |
| 8016 | 33 |
| 8017 | 44 |
| 8018 | 55 |
| 8019 | 66 |
| 801A | 77 |
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