??? 03/03/05 14:40 Read: times |
#88984 - Picky, picky, but no such thing! Responding to: ???'s previous message |
Michal Hupka said:
As Andy and Neil said on "classic" 8051 (or 8052) if you write the 1 to bit in register that match pin on microcontroller, it is setted as an input pin. That was Andy & Neil; now here's Andy Neil! Actually, there is nothing to set a standard 8051 pin as an input; all pins are always bidirectional. However, if you write a '0' to a pin, it turns the open-drain driver ON and there is no way that anything external can ever force it to anything other than '0' Therefore the input will just read '0' - irrespective of the external signal you might wish to read. But If you write a '1' to a pin, it turns the open-drain driver OFF and so an external signal can take the pin either high or low - and the input can read the state of the external signal. The is all explained in Chapter 3 of the "bible" for the 8051: Chapter 3 - 80C51 Family Hardware Description: http://www.semiconductors.philips.com/acrobat/v...WARE_1.pdf Start reading at p2, "Port Structure and Operation" and pay particular attention to Figures 4 & 5 |
Topic | Author | Date |
on 8051 settings pins as input or output | 01/01/70 00:00 | |
re: setting pins as input or output | 01/01/70 00:00 | |
thanks | 01/01/70 00:00 | |
Do you not | 01/01/70 00:00 | |
It's depending on chip | 01/01/70 00:00 | |
depending on chip | 01/01/70 00:00 | |
No reason for negative Karma point | 01/01/70 00:00 | |
fine | 01/01/70 00:00 | |
not first post, not first time asked | 01/01/70 00:00 | |
Picky, picky, but no such thing! | 01/01/70 00:00 | |
oh, I did just that | 01/01/70 00:00 | |
Don't try this at home... | 01/01/70 00:00 | |
Maybe it still works... | 01/01/70 00:00 | |
Eh??? | 01/01/70 00:00 | |
It's a joke, don't take it too literaly | 01/01/70 00:00 | |
Sorry | 01/01/70 00:00 | |
My english is still so poor...![]() | 01/01/70 00:00 |