| ??? 04/18/08 22:50 Read: times |
#153697 - From the datasheet Responding to: ???'s previous message |
When the MC writes "1" in one pin, and you have a load (led, resistor, etc) connected to ground, one says that that pin "sources" current. Inversely, writing "0" and connecting a load from Vcc, the pin "sinks" current.
The AT89C51, ports P1 to P3, can "source" 60uA, but the pin voltage can be as low as 2.4V. Under DC Characteristics in the Datasheet can check by youself. So, if you need to light a led, 60uA is too low. You can use some buffer (transistor as emitter-follower, for example) or invert the logic, connecting the led anode to Vcc and the cathode to the pin. When the MC writes "0" to the pin, it can "sinks" as much as 1mA. Check the datasheet: http://www.atmel.com/atmel/acrobat/doc0265.pdf |
| Topic | Author | Date |
| need help....8051 output voltages... | 01/01/70 00:00 | |
| Which port? | 01/01/70 00:00 | |
| thank Daniel but,,,, | 01/01/70 00:00 | |
| i`'m using at89c51 | 01/01/70 00:00 | |
| From the datasheet | 01/01/70 00:00 | |
| thank you | 01/01/70 00:00 | |
| made it a FAQ | 01/01/70 00:00 | |
| What? The hint to have a look at datasheet? | 01/01/70 00:00 | |
| OK I added that, too | 01/01/70 00:00 | |
| And this FAQ | 01/01/70 00:00 | |
| try this | 01/01/70 00:00 | |
| Rather useless | 01/01/70 00:00 | |
| Re-Kai Klaas | 01/01/70 00:00 | |
LED connection | 01/01/70 00:00 |