At 2002-11-06 06:08 -0800, Elbert Smit wrote:
>it has the advantage that the processor does not
>have to deal with the additional idle characters.

If I remember correctly most UART's will filter
these characters out, so it doesn't bother the
processor.

Probably the main disadvantages of synchronous
datacommunication are:
- you need one or two seperate clock-lines or
  you need to extract the clock rate from the
  data so you need some sort of PLL and you
  need to make sure that there are ones and
  zeros in every n samples (n being 16 or so)
- you can't use the sync-character within your
  data, so you'll need an extra driver layer
  if you don't want to burden the application
  programmers with this problem

I'm not really a datacom expert although I have
programmed for a system with 200 posts connected
on an upto 1 km long line but I have never
encountered a synchronous implementation.
Perhaps it's useful in a medium that needs
0/1-changes anyway like magnetical disks or
in cases where the device at the other end
derives it's power from these changes.


Greetings,
Jaap

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