| ??? 07/23/05 08:18 Read: times |
#97870 - Settle Erik! Responding to: ???'s previous message |
Well apart from your poorly documented code that does not tell me much about what the code is trying to do, nor what you're initialising the 8255 to. Why don't you write some nice subroutines with names like: write_8255_control write_8255_porta read_8255_portb write_8255_portc mov a,#82h ;mode 0, port A,C outputs,Port B inputs call write_8255_control mov a,#aah call write_8255_porta ....... That way anyone else won't have to pull out the datasheet and figure out what the code is doing. Anyway, you've haven't told us exactly what cpu you're using - you may not have enough width on the write signal or if you're using external code memory, the value of P0 is going to change due to the bus operation. What have you done to check the operation? Have you checked the bus timing with an oscilloscope or logic analyser? |
| Topic | Author | Date |
| 8255 interfacing problem | 01/01/70 00:00 | |
| well.. | 01/01/70 00:00 | |
| 8255 interface problem | 01/01/70 00:00 | |
| If you must use 8255 | 01/01/70 00:00 | |
| My datasheet says..... | 01/01/70 00:00 | |
| Settle Erik! | 01/01/70 00:00 | |
| 8255 problem | 01/01/70 00:00 | |
| hardware | 01/01/70 00:00 | |
| adding to Steve.. | 01/01/70 00:00 | |
| Comment | 01/01/70 00:00 | |
| Relic | 01/01/70 00:00 | |
| that was not 8255 | 01/01/70 00:00 | |
| Actually.... | 01/01/70 00:00 | |
| ot: 825x in PC | 01/01/70 00:00 | |
| Parallel port | 01/01/70 00:00 | |
| NOoooooooooooooooooooo | 01/01/70 00:00 | |
| Ooops | 01/01/70 00:00 | |
| OK I give it up! :-) | 01/01/70 00:00 | |
| Just like | 01/01/70 00:00 | |
| 8255 in original PC | 01/01/70 00:00 | |
| If I did not keep up with the times and | 01/01/70 00:00 | |
| Do your kids drive Segway? | 01/01/70 00:00 | |
| the real problem is not that the 82xx is | 01/01/70 00:00 | |
| Erik - A history lesson | 01/01/70 00:00 | |
| ok, even further back | 01/01/70 00:00 | |
| Picky, picky | 01/01/70 00:00 | |
| are we getting there now? | 01/01/70 00:00 | |
Oh altight then :-) | 01/01/70 00:00 | |
| More info needed | 01/01/70 00:00 | |
| Pull up resistors. | 01/01/70 00:00 | |
| Pullups | 01/01/70 00:00 | |
| no can do | 01/01/70 00:00 | |
| Yes he can! | 01/01/70 00:00 | |
| does not make it current | 01/01/70 00:00 | |
| my opinion... | 01/01/70 00:00 | |
| did you not read | 01/01/70 00:00 | |
| Nope | 01/01/70 00:00 | |
| 8255 PROBLEM | 01/01/70 00:00 | |
| 10 Points | 01/01/70 00:00 |