| ??? 07/23/05 20:07 Read: times |
#97884 - If you must use 8255 Responding to: ???'s previous message |
P Ravi said:
portA is supposed to display AAh but it is showing 00h
portC is supposed to display 55h but it is ffh why it is happening pl suggest Because you didn't read datasheet. You didn't follow timing diagrams and sequence of the signals. org 00h
; This block of code is to configure 8255
setb 8255_RD
setb 8255_a0
setb 8255_a1
clr 8255_CS <--------------- CS=0 should be here
mov p0,#082h
clr 8255_WR
setb 8255_WR
setb 8255_CS
; display aah at portA
clr 8255_a0
clr 8255_a1
clr 8255_CS <--------------- missing here is CS=0
mov p0,#0aah
clr 8255_WR
setb 8255_WR
setb 8255_CS
; display 55h at portC
clr 8255_a0
setb 8255_a1
clr 8255_CS <--------------- missing here is CS=0
mov p0,#055h
clr 8255_WR
setb 8255_WR
setb 8255_CS
sjmp$
Ravi If this does not work, you need to pay attention on timing of the signals. Remember 8255 is a slow device. This code has been posted using pre and /pre tags. Does it look better now? |
| 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 |