| ??? 03/27/05 05:08 Read: times |
#90471 - Cutting teeth... Responding to: ???'s previous message |
During the early years of microprocessors it was known in circles of serious engineers that standard recommended R/C reset circuits were trash. I recall one instance at a start-up company that I was a partner in we had purchased a new OEM keyboard design from Keytronics. This keyboard would not work about 20% of the time when the equipment was turned ON. I opened the keyboard up and found that its 8048 microcontroller was not getting a good reset from an R/C circuit. It was required to replace the R/C with a small comparator circuit and some resistors and a couple of diodes and a transistor. After that we tested the thing and it powered up and operated correctly over 1000's of tests. It did not take long to convince the engineer at Keytronics that they had sold us a bucket of junk keyboard and they re-worked the PCBA to include the new reset circuit. If only back in those early 1980's days we could have had one of the types of small cheap supervisor/brownout manager chips that are available today!!
It is experiences like this story that make most seasoned engineers that I know say that they will never design without a proper RESET manager chip. I know that I think that way!! On top of that I still ALWAYS use a standalone device for this purpose. I've been on the "fix it end of the stick" one too many times when a non-seasoned engineer has tried to make either an external R/C reset work or has believed the manufacturer when they claim how well their on-chip reset works. Designs have come to me for software or firmware and time after time I find that the turn-on is unreliable and then I have to re-work the board with a proper reset supervisor just to get myself through the development cycle !!! Michael Karas |
| Topic | Author | Date |
| What do you think could happen if... | 01/01/70 00:00 | |
| The 10k from RST to GND | 01/01/70 00:00 | |
| Random resets.. | 01/01/70 00:00 | |
| Dogma. | 01/01/70 00:00 | |
| Oh yea ? | 01/01/70 00:00 | |
| Hmm | 01/01/70 00:00 | |
| brown outs | 01/01/70 00:00 | |
| Obscure | 01/01/70 00:00 | |
| RC Reset circuits. | 01/01/70 00:00 | |
| Something more to it ... | 01/01/70 00:00 | |
| ad wars between Maxim and Microchip | 01/01/70 00:00 | |
| Cutting teeth... | 01/01/70 00:00 | |
| recommend brown out detectors | 01/01/70 00:00 | |
| Which depends on for what.. | 01/01/70 00:00 | |
| built-in reset | 01/01/70 00:00 | |
| Re: Built in brown out? | 01/01/70 00:00 | |
| Better than I did.... | 01/01/70 00:00 | |
| Thanks, Michael. | 01/01/70 00:00 | |
| Why | 01/01/70 00:00 | |
| Other stuff ? | 01/01/70 00:00 | |
| many reasons | 01/01/70 00:00 | |
| Thats not correct. | 01/01/70 00:00 | |
| speak with forked tongue | 01/01/70 00:00 | |
| I agree | 01/01/70 00:00 | |
| re: dogma | 01/01/70 00:00 | |
| ESD events and EMI | 01/01/70 00:00 | |
| Re: Random resets. | 01/01/70 00:00 | |
| Lets not reject the obvious! | 01/01/70 00:00 | |
| no R | 01/01/70 00:00 | |
| RC-circuits are bullshit!! | 01/01/70 00:00 | |
| RC-circuits are bullshit!! | 01/01/70 00:00 | |
| Reset Capacitor | 01/01/70 00:00 | |
| You missed the question! | 01/01/70 00:00 | |
| Why guessing? | 01/01/70 00:00 | |
| RE:Why Guessing | 01/01/70 00:00 | |
| Timing | 01/01/70 00:00 | |
| Update | 01/01/70 00:00 | |
| not necessarily the reset | 01/01/70 00:00 | |
| Other derivatives | 01/01/70 00:00 | |
| if no cap | 01/01/70 00:00 | |
| No Cap | 01/01/70 00:00 | |
| not just a cap, but the right cap | 01/01/70 00:00 | |
| Which cap? | 01/01/70 00:00 | |
| depends | 01/01/70 00:00 | |
| Yes Cap | 01/01/70 00:00 | |
| directly | 01/01/70 00:00 | |
| RE:Directly | 01/01/70 00:00 | |
| yes | 01/01/70 00:00 | |
| Absolutely ! | 01/01/70 00:00 | |
| Update - ESD Problem? | 01/01/70 00:00 | |
| some ways | 01/01/70 00:00 | |
| some ways - more detail please | 01/01/70 00:00 | |
| details | 01/01/70 00:00 | |
| Car induction coil | 01/01/70 00:00 | |
| ESD Problem | 01/01/70 00:00 | |
| Physical Separation | 01/01/70 00:00 | |
| Few Ideas | 01/01/70 00:00 | |
| Re: Few Ideas | 01/01/70 00:00 | |
| Check your external ground | 01/01/70 00:00 | |
| Ya. | 01/01/70 00:00 | |
| now that you are willing | 01/01/70 00:00 | |
| RE:Now that you are willing | 01/01/70 00:00 | |
| alot easier when you know what your look | 01/01/70 00:00 | |
| Not as bad as initially thought. | 01/01/70 00:00 | |
| ground loop | 01/01/70 00:00 | |
| RE: Ground Loop | 01/01/70 00:00 | |
| sound | 01/01/70 00:00 | |
| RE: Ground Loop | 01/01/70 00:00 | |
| It is a loop AND | 01/01/70 00:00 | |
| It's a loop and a flop | 01/01/70 00:00 | |
| no shield can help you there | 01/01/70 00:00 | |
| Kind of machine | 01/01/70 00:00 | |
| so your testbench setup should be OK | 01/01/70 00:00 | |
| Failures | 01/01/70 00:00 | |
| in that case | 01/01/70 00:00 | |
| Materials | 01/01/70 00:00 | |
| could still be ground | 01/01/70 00:00 | |
| Noise resistance | 01/01/70 00:00 | |
| you will not find that | 01/01/70 00:00 | |
| What can be found? | 01/01/70 00:00 | |
| tough these days | 01/01/70 00:00 | |
| Glue ? | 01/01/70 00:00 | |
| No Glue | 01/01/70 00:00 | |
| lesse some pictures. | 01/01/70 00:00 | |
| LOL | 01/01/70 00:00 | |
| Nope | 01/01/70 00:00 | |
| Let the fun begin! | 01/01/70 00:00 | |
| Confession | 01/01/70 00:00 | |
| Confession | 01/01/70 00:00 | |
| Ah. | 01/01/70 00:00 | |
| Not that bad | 01/01/70 00:00 | |
| HAr to see but | 01/01/70 00:00 | |
| Wiring & Filter | 01/01/70 00:00 | |
| Maybe a little better pictures here | 01/01/70 00:00 | |
| nice | 01/01/70 00:00 | |
| Oops - try again | 01/01/70 00:00 | |
| Uh Oh | 01/01/70 00:00 | |
| Yep | 01/01/70 00:00 | |
| Don't ground both ends of shield | 01/01/70 00:00 | |
| bonding | 01/01/70 00:00 | |
| RE: Bonding | 01/01/70 00:00 | |
| Useless.... | 01/01/70 00:00 | |
| Better Pix yet? | 01/01/70 00:00 | |
| Re: Better Pics Yet? | 01/01/70 00:00 | |
| DETAILS... | 01/01/70 00:00 | |
| Nothing hiding here! | 01/01/70 00:00 | |
| !!!!! | 01/01/70 00:00 | |
| I don't think so. | 01/01/70 00:00 | |
| !! | 01/01/70 00:00 | |
| Grounding. | 01/01/70 00:00 | |
| Grounding | 01/01/70 00:00 | |
| Prahlads points | 01/01/70 00:00 | |
| Clarification | 01/01/70 00:00 | |
| Clarification | 01/01/70 00:00 | |
| Update | 01/01/70 00:00 | |
| au contraire | 01/01/70 00:00 | |
| The answer may be on the horizon | 01/01/70 00:00 | |
| not the voltage, but the change | 01/01/70 00:00 | |
| Have a look see | 01/01/70 00:00 | |
| I do not know how good | 01/01/70 00:00 | |
| 7805 Starving | 01/01/70 00:00 | |
| it will go HOT | 01/01/70 00:00 | |
| Heatsink | 01/01/70 00:00 | |
or it's possible | 01/01/70 00:00 |