| ??? 05/02/07 08:37 Read: times |
#138440 - why not? Responding to: ???'s previous message |
Per Guldmann said:
From the DS89C430/440/450 spec. sheet:
Output low voltage Port 1 and 3: 0.15V at IOL 1.6 mA So you cant drive a led directly. But, why not? Today's high-efficiency LEDs give out enough light at 1mA, certainly much more than needed for simple indication of state, especially under controlled laboratory conditions (read: no direct sunlight). Andy Neil said:
That 1.6mA is a Test Condition for measuring Vol - it is not a rating for the pin's current capability! Given there are no other data, IMHO it is safe to assume the pin _withstands_ any current resulting from application of any voltage within the range given by the Absolute Maximum ratings. This should not come as a surprise for a modern driver NMOS with typical ON resistance of some 100 Ohm. Although in a commercial design I certainly wouldn't do it without explicitly asking the manufacturer, I assume it would be quite safe to put there a LED directly without any series resistance (and expect around 3mA current flow into it). JW |
| Topic | Author | Date |
| Very stubborn UARTs... | 01/01/70 00:00 | |
| Keil gives error on your construct | 01/01/70 00:00 | |
| Re: error | 01/01/70 00:00 | |
| a guess | 01/01/70 00:00 | |
| Re: guess | 01/01/70 00:00 | |
| humm humm | 01/01/70 00:00 | |
| re: humming | 01/01/70 00:00 | |
| PS | 01/01/70 00:00 | |
| have you tried the simulator? | 01/01/70 00:00 | |
| Re: LED | 01/01/70 00:00 | |
| HUH??? | 01/01/70 00:00 | |
| again a HLL habit, isn't it... | 01/01/70 00:00 | |
| 2 possibilities | 01/01/70 00:00 | |
| Whoops. | 01/01/70 00:00 | |
| Dummy Interupt | 01/01/70 00:00 | |
| agreed, I do it like this | 01/01/70 00:00 | |
| Niiice | 01/01/70 00:00 | |
| you could solve a lot of problems if.... | 01/01/70 00:00 | |
| Thanks, but... | 01/01/70 00:00 | |
| Back to square one? | 01/01/70 00:00 | |
| blinkenlight | 01/01/70 00:00 | |
| Get a \'scope! | 01/01/70 00:00 | |
| More hints | 01/01/70 00:00 | |
| Re: hints | 01/01/70 00:00 | |
| I am sure it is published | 01/01/70 00:00 | |
| Gah. | 01/01/70 00:00 | |
| read the right spec | 01/01/70 00:00 | |
| specs | 01/01/70 00:00 | |
| Not a spec | 01/01/70 00:00 | |
| why not? | 01/01/70 00:00 | |
| Proviso | 01/01/70 00:00 | |
| just a small remark | 01/01/70 00:00 | |
| oh, yes, you can | 01/01/70 00:00 | |
| Huzzah! | 01/01/70 00:00 | |
| value of KISS | 01/01/70 00:00 | |
| I find that hard to beleive! | 01/01/70 00:00 | |
| Okay, so | 01/01/70 00:00 | |
| I thotoughly agree with you there! | 01/01/70 00:00 | |
| Further details | 01/01/70 00:00 | |
| You\'re not finished yet | 01/01/70 00:00 | |
| Lessons | 01/01/70 00:00 | |
| \"does have it all\" is of no good | 01/01/70 00:00 | |
Thanks for the update | 01/01/70 00:00 |