[rescue] SS Classic Serial ports
mcguire at neurotica.com
Sat Apr 26 13:29:51 CDT 2003
On Saturday, April 26, 2003, at 02:20 PM, Scott Newell wrote:
>> Now, that's not because the chips are so terrible, but because Sun did
>> odd things in the implementation. They use seperate clocks for in and
>> out, which drift and every N frames cause an error at high speeds.
> Hmmm... Do you mean that Sun ignored the internal baud rate
> generators on
> the 8530 uarts, and generated separate clocks for the shift registers
> through the RTxCA, RTxCB, TRxCA, and TRxCB pins? I don't think so.
> uart has a baud rate generator for each channel, and the clocks for tx
> rx on a single channel are shared. Looking through the OpenBSD
> source, it
> sure appears to me that the default situation is to use the internal
> rate generators.
I think the actual issue here is the use of a poorly-chosen
combination of Z8530 crystal frequency and main divider settings which
trashes the rates for high-speed use.
St. Petersburg, FL
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