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8085 program to add two consecutive bytes of an array
Here we will see how we can add two consecutive elements in an array using 8085.
Problem Statement
Write 8085 program to add two consecutive elements of an array and store them in the same location. The carry will be placed at bottom of the other byte. The numbers are stored from location 8001. The size of array is stored at 8000.
Discussion
Here we will solve this problem by using one subroutine. That will add two consecutive numbers and stored them into correct position. That subroutine will be called multiple times to add all consecutive pairs. The task will be followed half of the number of elements. So we are taking the count, then rotate it to the right to make it half. We are rotating through carry. if the carry is already high it may store different result, so we are clearing the carry by using STC and CMC instructions.
Input
| Address | Data |
|---|---|
| … | … |
| 8000 | 0A |
| 8001 | E9 |
| 8002 | D3 |
| 8003 | 61 |
| 8004 | AD |
| 8005 | 2A |
| 8006 | 1F |
| 8007 | 5D |
| 8008 | A6 |
| 8009 | A9 |
| 800A | 35 |
| … | … |
Flow Diagram
Program
| Address | HEX Codes | Labels | Mnemonics | Comments |
|---|---|---|---|---|
| F000 | 21, 00, 80 | | LXI H,8000 | Point to get array size |
| F003 | 7E | | MOV A,M | load array size into memory |
| F004 | 37 | | STC | set carry flag |
| F005 | 3F | | CMC | complement carry flag |
| F006 | 0F | | RRC | rotate right through carry |
| F007 | 47 | | MOV B,A | Store A into B |
| F008 | 23 | LOOP | INX H | point to next location |
| F009 | CD, 11, F0 | | CALL PADD | call Pair Add subroutine |
| F00C | 05 | | DCR B | Decrease B by 1 |
| F00D | C2, 08, F0 | | JNZ LOOP | jump to loop |
| F010 | 76 | | HLT | Terminate the program |
| F011 | 0E, 00 | PADD | MVI C,00H | clear C flag |
| F013 | 7E | | MOV A,M | load first number from memory to A |
| F014 | 23 | | INX H | point to next location |
| F015 | 86 | | ADD M | add A and memory element |
| F016 | D2, 1A, F0 | | JNC STORE | if carry is not set, jump to STORE |
| F019 | 0C | | INR C | else increase C by 1 |
| F01A | 71 | STORE | MOV M,C | store C into memory |
| F01B | 2B | | DCX H | point to previous location |
| F01C | 77 | | MOV M,A | store A into memory |
| F01D | 23 | | INX H | point to next location |
| F01E | C9 | | RET | return from subroutine |
Output
| Address | Data |
|---|---|
| … | … |
| 8001 | BC |
| 8002 | 01 |
| 8003 | 0E |
| 8004 | 01 |
| 8005 | 49 |
| 8006 | 00 |
| 8007 | 03 |
| 8008 | 01 |
| 8009 | DE |
| 800A | 00 |
| … | … |
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