[rescue] SS Classic Serial ports

Dave McGuire 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.  
> The
> uart has a baud rate generator for each channel, and the clocks for tx 
> and
> 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 
> baud
> 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.


Dave McGuire
St. Petersburg, FL

More information about the rescue mailing list