Email: Password: Remember Me | Create Account (Free)

Back to Subject List

Old thread has been locked -- no new posts accepted in this thread
???
04/24/07 12:31
Read: times


 		 #137876 - sometimes two wants do not jive
Responding to: ???'s previous message
sometimes two wants do not jive

Atmel MCU with PLL? ... in fact i want to use simpler AT89SXX series.

If you want an internal PLL you need another uC, if you want to use Atmel, you may be able to do something with an external PLL, there are many around, if I recall, there is one in the CD40xx series, I do not recall if it is fast enough.

The issue of double clock for a uC is not 'simple', when switching all kinds of glitches may (will) occur.

Now, re 'static switching':

If you, as you propose, use a mechanical switch and switch only at power off, you may get side effects from stray capacitances bringing the other crystal to interfere,

What i would do, if all I needed was to change frequency occasionally and at power off would be to use a socketed crystal.

Erik

List of 31 messages in thread
TopicAuthorDate
two crystals            01/01/70 00:00      
   Crystal connections            01/01/70 00:00      
      wires very very short            01/01/70 00:00      
         Youd be better off with a pair of DIY oscillators            01/01/70 00:00      
            why not use a derivative with a PLL?            01/01/70 00:00      
               What's a PPL?            01/01/70 00:00      
                  Phase Locked Loop            01/01/70 00:00      
                     It's not a very general sort of PLL            01/01/70 00:00      
                        apples and oranges            01/01/70 00:00      
                           Consider why one would want that ...            01/01/70 00:00      
                        PLL lock timing            01/01/70 00:00      
                           support droids didn't notice that ...            01/01/70 00:00      
                              .. err make that "jibe" : -)            01/01/70 00:00      
                     Atmel MCU with PLL?            01/01/70 00:00      
                        sometimes two wants do not jive            01/01/70 00:00      
                        sadly atmel 8051 derivatives dont            01/01/70 00:00      
            Am I right Richard?            01/01/70 00:00      
               What I meant ...            01/01/70 00:00      
   Koosha, we need an answer            01/01/70 00:00      
      What is in my mind...            01/01/70 00:00      
         why a switch ? It will give you all kins of proble            01/01/70 00:00      
         Maybe use a jumper instead of a switch?            01/01/70 00:00      
            better, yes, as good as none no.            01/01/70 00:00      
            it's commonly used.            01/01/70 00:00      
               all the story!            01/01/70 00:00      
                  Capacitor size            01/01/70 00:00      
                  whare is the uC?            01/01/70 00:00      
                     The uC is in the ZIF socket            01/01/70 00:00      
                  not this type of switch, please            01/01/70 00:00      
                  consider ALL the components!            01/01/70 00:00      
   Thank you!            01/01/70 00:00      

Back to Subject List