[rescue] SS Classic Serial ports

Scott Newell newell at cei.net
Sat Apr 26 16:03:14 CDT 2003

At 03:58 PM 4/26/2003 -0400, Charles Shannon Hendrix wrote:
>On Sat, Apr 26, 2003 at 02:29:51PM -0400, Dave McGuire wrote:
>>   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.
>That's one issue, yes.  The other is a very small buffer and little
>or no DMA use.

And interrupt load.  

>But some of the serial hackers also mentioned seperate clocks.
>If you google for sun serial port issues, you should find a conversation
>between der Mouse and a few others about this, maybe 3 years ago.  Can't
>remember exactly.

I read the thread linked at:

There was some discussion about seperate clocks, but they're discussing the
devices (say, a sparc box and a terminal) at each end of the cable not
sharing a common clock, not that a port on the onboard uart is running two
different clocks for tx and rx.  Of course, this is the situation with
almost every async comm link, not something specific to the Sun

Wonder if I could get 115.2k out of my ss2 (for my webpal hacking) by going
to an external baud rate clock at the sparc...


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