| ??? 05/28/05 12:37 Read: times |
#94043 - Additional Comment on Rise Time Responding to: ???'s previous message |
You may respond that you do not really care about the rise time of the signal at the output of the opto coupler. There are a few instances where this can be important however. If your software is using a time sampled technique to monitor an input and wants to reliably detect the opto-coupler ON to OFF transition (ie sampled low in one sample time followed by sampled high in next sample time) then a faster rise time can be highly desirable. A slow signal transition time causes the 8051 input pin to be in the no-mans-land between VIL and VIH for a long time. If a timed sample comes right at the time the signal is in this zone the software may not correctly read the signal level. This could lead to an improperly detected transition. The problem could be really bad if the signal stays in the no-mans-land through the time of several of the timed sample periods.
Michael Karas |
| Topic | Author | Date |
| CNX83: application examples? | 01/01/70 00:00 | |
| HOW | 01/01/70 00:00 | |
| did you find some in a drawer | 01/01/70 00:00 | |
| I know they're quite old... | 01/01/70 00:00 | |
| Better | 01/01/70 00:00 | |
| Schmitt Trigger | 01/01/70 00:00 | |
| nothing wrong - but | 01/01/70 00:00 | |
| Not working, Erik | 01/01/70 00:00 | |
| Pullup Or Not | 01/01/70 00:00 | |
| Additional Comment on Rise Time | 01/01/70 00:00 | |
| Confustion maybe? | 01/01/70 00:00 | |
| Yes, you need on PCF8574 | 01/01/70 00:00 | |
| No hijacking at all!!! ;-) | 01/01/70 00:00 | |
| Walks like a duck? Quacks like a duck? | 01/01/70 00:00 | |
| Yes, I do have quite a few ducks... | 01/01/70 00:00 | |
| Correct? | 01/01/70 00:00 | |
| Correct !! | 01/01/70 00:00 | |
| you must have edited | 01/01/70 00:00 | |
| I didn't do anything... | 01/01/70 00:00 | |
I do not know | 01/01/70 00:00 |