| ??? 04/05/07 13:00 Read: times |
#136680 - It is normal Responding to: ???'s previous message |
Hi Mike. It is not the crystal (at least directly). When you pull reset up, oscillator does not stop. But when you let it down, uC starts working: address and data lines, WD and RD toggle, and the spectrum of signals that change fast (with large dv/dt) like those, is almost like white noise, at least for your radio.
There are few chances for reducing the EMI that the uC produces.Good decoupling Vcc technics, short lines, specially for those that toggle (WD, RD, P0 and P2 if using external memory), and only internal memory use can help. But I repeat: crystal is OK. It produces only a 3.6MHz (and few armonics) signal. All the rest is the result of the fast switching signals normally present in any uC board. Regards, Daniel |
| Topic | Author | Date |
| my board creates white noise. | 01/01/70 00:00 | |
| Everything is a source of noise... | 01/01/70 00:00 | |
| Me too. | 01/01/70 00:00 | |
| It is normal | 01/01/70 00:00 | |
| Don't add resistors to the crystal | 01/01/70 00:00 | |
| RF-emission spectrum was discussed earlier... | 01/01/70 00:00 | |
| It's not the crystal | 01/01/70 00:00 | |
| what other lines? | 01/01/70 00:00 | |
| any | 01/01/70 00:00 | |
| AM carriers | 01/01/70 00:00 | |
| All other lines | 01/01/70 00:00 | |
one of the reasons for internal memory | 01/01/70 00:00 |