| ??? 01/22/05 23:37 Read: times |
#85589 - A little history Responding to: ???'s previous message |
Whilst a little 'left of field', pullups go back to the days of ttl (and maybe even before) where most inputs were active low due to the fact that the TTL input would float high. So us 'old timers' will normally do things this way - even if it is not necessary. Obviously, the design of the 8051 compels us to do it this way anyhow. |
| Topic | Author | Date |
| Inputs | 01/01/70 00:00 | |
| Opto | 01/01/70 00:00 | |
| Opto input | 01/01/70 00:00 | |
| Optocoupler Designer’s Guide | 01/01/70 00:00 | |
| What type of opto? | 01/01/70 00:00 | |
| pulling high | 01/01/70 00:00 | |
| Why??? | 01/01/70 00:00 | |
| Misleading.... | 01/01/70 00:00 | |
| OK, clearer | 01/01/70 00:00 | |
| I must be stupid... | 01/01/70 00:00 | |
| you are not | 01/01/70 00:00 | |
| Heres Why | 01/01/70 00:00 | |
| Not quite so. | 01/01/70 00:00 | |
| Pull-downs must be much smaller! | 01/01/70 00:00 | |
| OK you are right. | 01/01/70 00:00 | |
A little history | 01/01/70 00:00 | |
| Link... | 01/01/70 00:00 | |
| use opto-coupler as NPN | 01/01/70 00:00 | |
| Thank you All, & a question for Kai | 01/01/70 00:00 | |
| Opto to pull-down signal | 01/01/70 00:00 |