| ??? 05/03/08 20:48 Modified: 05/03/08 20:48 Read: times |
#154355 - This would all be perfectly obvious if only you\'d Responding to: ???'s previous message |
READ THE DATASHEET!
It's explained in painstaking detail in the "bible," to which there are links all over the place, particularly on the main page of this website. Unless it's you're homework assignment, and you're not willing to do it yourself, there's no reason to question such things, as they are simple realities which won't be changed just because someone doesn't like them. I'd suggest you find and read the datasheet for the MC6821, to get a picture of how Motorola thought I/O should be handled. You might want to compare the way in which the 805x handles its ports vs. how the MC68HC11 or the MC6801 (if you can find a datasheet) is set up. I think you'll find the 805x setup to be remarkably simple by comparison. RE |
| Topic | Author | Date |
| P0 pull up resistors | 01/01/70 00:00 | |
| ports structure | 01/01/70 00:00 | |
| More Port 0 history | 01/01/70 00:00 | |
| Of course, there is a reason for it... | 01/01/70 00:00 | |
| Port 0 Pullups WHY??? | 01/01/70 00:00 | |
| P0 is multiplexed for input/output; P2 is not | 01/01/70 00:00 | |
| This would all be perfectly obvious if only you\'d | 01/01/70 00:00 | |
| See this thread | 01/01/70 00:00 | |
| Scary Bible | 01/01/70 00:00 | |
| Only In Some Cases.... | 01/01/70 00:00 | |
| Directly connecting the base will hardly work! | 01/01/70 00:00 | |
| Hardly is correct.... | 01/01/70 00:00 | |
| what about a darlington? | 01/01/70 00:00 | |
| Will also turn off the weak pull-up... | 01/01/70 00:00 | |
| The high state is adequate for some things | 01/01/70 00:00 | |
OH | 01/01/70 00:00 |