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???
07/07/04 21:55
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#73757 - RE: Hi speed serial commn revisited
Responding to: ???'s previous message
With a 11.0592 crystal and using serial interrupt , and a ring buffer for temporary storage ,is it likely that if the code size is big enough the serial interrupts come rapidly enough to overwrite the buffer ?
absolutely, just figure - you have ~100usec ~50 instructions per byte.

If there is sufficient RAM avlbl on chip ( 89C51RD2xx ) , how does one optimise ( calculate ) the size of the ring buffer to avoid this ?
I would always have a ring buffer large enough to hold one burst.
Calculation can be quite hairy e.g. how often does a timer interrupt delay the process, e.g. usually the processing time for a length byte will not be the same as for a data byte etc

When J Guy says that 18.432 MHz will give the same baud rate and be faster , what does it mean ? 115200 baud should be the same whether 18.432 or 11.0592 . Or is it just that he means the code will be processed faster so that buffer overwrite does not happen .
so that buffer overwrite is less likely to happen.

If a board is working well with a 12 MHz chip , will there be any problems if I pluck it out and replace with a 20 MHz , asuuming there are no timing implications on the software side ?
usually no problem, but of this is not a (4 layer) PCB but components wired together, I would not trust it. Also things, like decoupling caps and the distance they are from the chips, become more important the higher the frequency.


To run at 115k, I would, at least, use a 6 clocker at 18.432 MHz

Erik

List of 7 messages in thread
TopicAuthorDate
Hi speed serial commn revisited            01/01/70 00:00      
   RE: Hi speed serial commn revisited            01/01/70 00:00      
      RE: Hi speed serial commn revisited            01/01/70 00:00      
         RE: Hi speed serial commn revisited            01/01/70 00:00      
      RE: Hi speed serial commn revisited            01/01/70 00:00      
   RE: Hi speed serial commn revisited            01/01/70 00:00      
   RE: Hi speed serial commn revisited            01/01/70 00:00      

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