| ??? 06/06/06 14:29 Read: times |
#117865 - Should I study more? Responding to: ???'s previous message |
I tried to understand Figure4 of 80C51_FAM_HARDWARE.PDF from Erik's "Bible". It is titled "8051 Port Bit Latches and I\O Buffers". I hope this is want you wanted me to take a look at. But, again I fail to understand it completely, because I don’t understand the diagrams and the symbols therein. But from your explanations above, I can understand that there is a transistor somewhere inside the 8051 which controls whether a port happens to be an input or output port at that instant. It is this transistor (and not the value written on the pin; at least not directly!) that decides the I\O mode of the pin. But I am still not clear what will happen if I do some thing like this:
MOV P2,#1 ;writing HIGH to bit 0 of Port2
MOV P2,#0 ;Writing LOW to bit 0 of Port2
Is this sequence of instructions permitted, and will it serve the purpose? Also i want to ask, if you think I should understand, the underlying hardware seriously before I venture any further? |
| Topic | Author | Date |
| Help Understanding AT89C51 Datasheet | 01/01/70 00:00 | |
| logic gain and other | 01/01/70 00:00 | |
| Should I study more? | 01/01/70 00:00 | |
| do you have any hardware knowledge | 01/01/70 00:00 | |
| No hardware knowledge | 01/01/70 00:00 | |
| what purpose? | 01/01/70 00:00 | |
| Purpose | 01/01/70 00:00 | |
| many get confused by this | 01/01/70 00:00 | |
| Got it ! | 01/01/70 00:00 | |
| per-pin, per-port, and whole-chip limits | 01/01/70 00:00 | |
| strictly speaking... | 01/01/70 00:00 | |
| Slight oversimplification | 01/01/70 00:00 | |
| it used to be DC, now it is AC | 01/01/70 00:00 | |
"per pin" | 01/01/70 00:00 | |
| Good post! | 01/01/70 00:00 | |
| Excellent Community | 01/01/70 00:00 | |
| have you read "the bible" | 01/01/70 00:00 | |
| Yes, I have started | 01/01/70 00:00 |