| ??? 02/22/08 07:43 Read: times Msg Score: -1 -1 Answer is Wrong |
#151286 - too big input resistors Responding to: ???'s previous message |
You have on P3.4 internal pull-up resistor and this input
will never see logic "0" with 470k. (0.4V-0.1V) (Vinputlow-Vttl_out) / 70microamp(input current P0)=4.2 kiloohm maximum. Use 2..4k or 74HC buffer if signal comes from other board. For port P0.7- 10microamp*470kiloohm=4.7Volt across input resistor due leakage/input current. So step down this resistor to 20..47 kiloohm. regards |
| Topic | Author | Date |
| check my interfacing scheme please? | 01/01/70 00:00 | |
| Schematic is not clear to me atleast | 01/01/70 00:00 | |
| too big input resistors | 01/01/70 00:00 | |
| of course, you will | 01/01/70 00:00 | |
| Judging from the picture on the home page ... | 01/01/70 00:00 | |
| the FAQ has it all | 01/01/70 00:00 | |
| my apologies | 01/01/70 00:00 | |
| No need to apologize, Brian... | 01/01/70 00:00 | |
| thank you | 01/01/70 00:00 | |
| nit really ... but | 01/01/70 00:00 | |
thank you | 01/01/70 00:00 | |
| dont know other way | 01/01/70 00:00 |