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8085 program to implement the following function (a*b) + (c*d)
Here we will see how to implement mathematical function using 8085.
Problem Statement
Write a program to implement the following function (a*b) + (c*d) and store the result in memory locations 8204 and 8205. Perform multiplication by using a subroutine. Here a, b, c and d numbers are stored at memory locations 8200H, 8201H, 8202H and 8203 respectively.
Discussion
Multiplication instruction is not present in the 8085. So we have to use subroutine to perform multiplication. In this subroutine, it takes number from memory pointed by HL pair, and return result into DE register pair. After multiplying two parts, the intermediate results are stored, then add them to get the final result.
Input
| Address | Data |
|---|---|
| … | … |
| 8200 | 02 |
| 8201 | 03 |
| 8202 | 04 |
| 8203 | 05 |
| … | … |
| Address | Data |
|---|---|
| … | … |
| 8200 | CA |
| 8201 | C6 |
| 8202 | C8 |
| 8203 | 64 |
| … | … |
Flow Diagram
Program
| Address | HEX Codes | Labels | Mnemonics | Comments |
|---|---|---|---|---|
| 8000 | 31, 00, 83 | START: | LXI SP, 8300 H | Initialize stack pointer SP = 8300 H |
| 8003 | 21, 00, 82 | | LXI H, 8200 H | Initialize memory pointer HL = 8200 H which is the starting data block address |
| 8006 | CD, 19, 80 | | CALL MULTI | Call Subroutine Multi.. It takes HL as the source data block pointer and returns result in DE register pair |
| 8009 | D5 | | PUSH D | Store result1 i.e. a * b |
| 800A | 23 | | INX H | Point to next data pair |
| 800B | CD, 19, 80 | | CALL MULTI | Call Subroutine Multi.. It takes HL as the source data block pointer and returns result in DE register pair |
| 800E | C1 | | POP B | Get result1in BC which at the top |
| 800F | E5 | | PUSH H | Store pointer |
| 8010 | EB | | XCHG | Get result2 in HL i.e. c * d |
| 8011 | 9 | | DAD B | HL= HL+BC (result1+result2: sum of products). So HL = a * b + c * d |
| 8012 | EB | | XCHG | Store result in DE and HL will be destination pointer |
| 8013 | E1 | | POP H | Restore the memory pointer |
| 8014 | 23 | | INX H | Point to destination address |
| 8015 | 73 | | MOV M, E | Store at HL, LSB of result (HL) = E |
| 8016 | 23 | | INX H | Point to the next location |
| 8017 | 72 | | MOV M, D | Store at HL, MSB of result (HL)=D |
| 8018 | 76 | | HLT | Stop |
| 8019 | 4E | MULTI: | MOV C, M | C = no1 |
| 801A | 23 | | INX H | HL= HL+1; point to next number |
| 801B | 46 | | MOV B, M | B = no2 |
| 801C | E5 | | PUSH H | Save HL register pair |
| 801D | 26, 00 | | MVI H, 00 H | H = 00; to track carry (carry register: will contain the MSB of result) |
| 801F | 3E, 00 | | MVI A, 00 H | A = 00 (Sum register) |
| 8021 | 80 | UP: | ADD B | A = A + B |
| 8022 | D2, 26, 80 | | JNC LOOP | Is carry = 1? If no go to loop |
| 8025 | 24 | | INR H | H = H + 1 |
| 8026 | 0D | LOOP: | DCR C | C = C – 1 |
| 8027 | C2, 21, 80 | | JNZ UP | Is Z = 0? If no go to up |
| 802A | 6F | | MOV L, A | Get sum in L from A (LSB of result) |
| 802B | EB | | XCHG | Get result in DE from HL |
| 802C | E1 | | POP H | Restore back HL register pair |
| 802D | C9 | | RET | Go back to main |
Output
| Address | Data |
|---|---|
| … | … |
| 8204 | 1A |
| 8205 | 00 |
| … | … |
| Address | Data |
|---|---|
| … | … |
| 8204 | 5C |
| 8205 | EA |
| … | … |
Updated on: 30-Jul-2019
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