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8085 program for running light with delays using lookup table.
Here we will see how we can implement running light with some delays using 8085.
Problem Statement
Write 8085 program to implement running light display with appropriate delays using lookup table stored from memory location 8100H on words.
Discussion
The patterns are stored at location 8100 onwards. We are using 8255 port IC to display the content in LED displays. After displaying, it calls the delay to wait for some time and call the next byte from memory to display. So the display pattern will be like below -
Program
| Address | HEX Codes | Labels | Mnemonics | Comments |
|---|---|---|---|---|
| 8000 | 31, 00, 82 | START: | LXI SP, 8200 H | Initializing the SP |
| 8003 | 0E, 15 | | MVI C, 14 H | Initializing the counter |
| 8005 | 21, 00, 81 | | LXI H, 8100 H | Pointing to the pattern IN-BUFFER |
| 8008 | 3E, 99 | | MVI A, CW | Load the CW in the accumulator |
| 800A | D3, 43 | | OUT 43 H | Output the CW to control register |
| 800C | 7E | AGAIN: | MOV A, M | Read pattern byte |
| 800D | D3, 41 | | OUT 41 H | Out at port B |
| 800F | CD, 20, 80 | | CALL DELAY | Calling the delay sub-routine |
| 8012 | 2C | | INR L | Pointing to the next location |
| 8013 | 0D | | DCR C | Decrement the counter |
| 8014 | C2, 0C, 80 | | JNZ AGAIN | If not exhausted go again |
| 8017 | 76 | | HLT | Stop |
| 8020 | C5 | DELAY: | PUSH B | Saving B. This delay subroutine uses 2 single registers A & D and 1 register pair BC |
| 8021 | F5 | | PUSH PSW | Saving PSW |
| 8022 | 16, 0F | | MVI D, 0F H | Loading counter for outer loop |
| 8024 | 01, 00, 10 | ST: | LXI B, 1000 H | Loading counter for inner loop |
| 8027 | 0B | L: | DCX B | Decrement inner counter |
| 8028 | 79 | | MOV A, C | If not exhausted go again for inner loop |
| 8029 | B0 | | ORA B | |
| 802A | C2, 27, 80 | | JNZ L | |
| 802D | 15 | | DCR D | Decrement outer counter |
| 802E | C2, 24, 80 | | JNZ ST | If not exhausted go again for outer loop |
| 8031 | F1 | | POP PSW | Restore PSW |
| 8032 | C1 | | POP B | Restore B |
| 8033 | C9 | | RET | Return to the calling program |
Updated on: 30-Jul-2019
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