| ??? 09/11/06 19:01 Read: times Msg Score: +2 +6 Informative -3 Overrated -1 Message Not Useful |
#124088 - P0 not low enough (0.85V) |
Hi,
An unusual post, this, with problem & solution in one go! I'm working on a hand-wired proto ("simple" serial-parallel converter to stretch a data bus). Initially, the processor wouldn't run at all, but finally it did (first warning, I guess). Then I could not get the P0 outputs low enough, even with just a pull-up (didn't forget those!). An activity led via a 74HCT04 on P0.6 flashed as required, serial out worked most of the time (warning 2?), but the 74HCT138s on the other P0 bits just wouldn't select anything. After searching here (not wishing to post before checking!), I finally got that intuitive flash that we all get from time-to-time (it needs 0V to pull down to 0V), & noticed that there was no 0V connected to the 89C52!! Works a treat now! Tears of joy (& pangs of hunger, too!). As usual, you just have to hang in there. It's only hardware & software, & it *always* works in the end! Regards, Richard in Belgium |
| Topic | Author | Date |
| P0 not low enough (0.85V) | 01/01/70 00:00 | |
| ? | 01/01/70 00:00 | |
| Not useful? Overrated?? | 01/01/70 00:00 | |
| Diodes | 01/01/70 00:00 | |
| A path to GND would still be needed | 01/01/70 00:00 | |
| paths to GND might be fatal | 01/01/70 00:00 | |
| Thanks for the tip | 01/01/70 00:00 | |
| Rather low ohmic path | 01/01/70 00:00 | |
| thanks | 01/01/70 00:00 | |
| if that is so | 01/01/70 00:00 | |
| P0 - all's well | 01/01/70 00:00 | |
| Another Thanks | 01/01/70 00:00 | |
| Richard, I hope you are well now | 01/01/70 00:00 | |
| not necessarily for long | 01/01/70 00:00 | |
| Aware of that! | 01/01/70 00:00 | |
| Isn't this whole thing rather silly? | 01/01/70 00:00 | |
| good practice, Richard... | 01/01/70 00:00 | |
| Nooooooo... | 01/01/70 00:00 | |
| Newbies aren't rigorous! | 01/01/70 00:00 | |
| That\'s one place where we can help them! | 01/01/70 00:00 | |
| still glad I posted this one! | 01/01/70 00:00 | |
| it's maybe better | 01/01/70 00:00 | |
| It's a silly mistake, but one we've all made! | 01/01/70 00:00 | |
the definition of experience: | 01/01/70 00:00 |