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???
10/17/05 12:15
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 		 #102483 - Not designed to drive additional loads
Responding to: ???'s previous message
Fausto said:
The XTAL clock OUTPUT is at a very low level (about 1V), and it can not drive a clock INPUT of another microcontroller, such as a small P87LPC764 that I used as bootloader with the previous AT89S53. Atmel told me to try 10pF capacitors on the crystal, or no caps at all, but it does not work.

Well, they gave you a bad recommedation! Decreasing or increasing the burden caps is always a "no-no", because this can heavily rise the drive level of crystal and result in a damage.
Feeding the oscillator output to other chips being spread over the board isn't a good idea either, because then a complex load develops, which can heavily erode integrity of oscillator signal. Built-in oscillator isn't designed to drive longer signal traces or additional capacitve loads, but only the crystal and its associated burden caps sitting extremely close to the oscillator and ground pins of micro.
Spend for each micro an individual crystal.

Kai

List of 26 messages in thread
TopicAuthorDate
AT89S8253: another couple of problems            01/01/70 00:00      
   Not designed to drive additional loads            01/01/70 00:00      
      a quote            01/01/70 00:00      
         The Facts of the real world.            01/01/70 00:00      
            who said "buy from digikey"            01/01/70 00:00      
            Think about it            01/01/70 00:00      
         Yes, but...            01/01/70 00:00      
            Indeed I did, but please quote all I sai            01/01/70 00:00      
               Sorry..            01/01/70 00:00      
                  no offense, just wanted to make clear            01/01/70 00:00      
                     I don't want to attak            01/01/70 00:00      
                        not you Fausto            01/01/70 00:00      
         What do you make, Erik?            01/01/70 00:00      
            a lot of questions, a lot of answers            01/01/70 00:00      
               why            01/01/70 00:00      
               Guaranteed parameters            01/01/70 00:00      
                  There are, indeed, such references. Howe            01/01/70 00:00      
                     So TF2 problem is a hardware bug            01/01/70 00:00      
                        absolutely            01/01/70 00:00      
            one (bad) try and a suggestion            01/01/70 00:00      
               Re: one (bad) try and a suggestion            01/01/70 00:00      
   Newbie question...            01/01/70 00:00      
      Central clock versus decentral clocks            01/01/70 00:00      
         I would never use multiple non-synchroni            01/01/70 00:00      
      already suggested            01/01/70 00:00      
   Latest news on bugs in 8253            01/01/70 00:00      

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