Re: IIGS 115,200 Baud Serial Port - How?

[schmidtd <schmidtd@my-deja.com>]

On Dec 29, 4:16 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:
> Hugh Hood wrote:
> > For many years, it's been generally accepted that the (2) IIGS built-in
> > serial ports (Zilog 8530 SCC chip) max out at 57,600 baud.
>
> > When pros like David Empson say so, I believe it.
>
> > And yet, along comes David Schmidt, with his ADTPro, and he's transferring
> > files at 115,200 baud from the IIGS modem port.
>
> Even more interesting is the trick suggested by Stephen Thomas (and
> reported here by me ;-), to skip the clock divider on the Super Serial
> Card to allow the 6551 ACIA to move data at 115,200 bps.
>
> The SCC has *always* been known to be capable of considerably higher
> rates, as, for example, when it is used to support AppleTalk.
Zoom, zoom.  :-)

I learned all I know from two sources... first, this source code:
http://www.apple2.org.za/gswv/a2zine/Utils/Z8530_SCCsamples_info.txt
and second, from the Zilog manual.  (Well, also from some early Darwin
code (< OSX) to support the SCC on earlier Mac hardware, but that's
largely redundant with the Zilog book.)