Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!um-math!hyc
From: hyc@math.lsa.umich.edu (Howard Chu)
Newsgroups: comp.sys.atari.st
Subject: Re: ST @ 38400 baud???
Message-ID: <665@stag.math.lsa.umich.edu>
Date: 31 May 89 19:50:08 GMT
References: <43609a62.14a1f@gtephx.UUCP> <1506@atari.UUCP> <8551@chinet.chi.il.us> <18870@cup.portal.com>
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In article <18870@cup.portal.com> BUGGS@cup.portal.com (William Edward JuneJr) writes:
>I've read recently about the Double Click serial port expansion box allowing
> the STs or Megas to operate to 38400 baud. Is this true?
>I definately want to know!!!
>I've been thinkin' of gettin' a USR dual standard(HST & V.32) modem for my BBS.
>It would be GREAT to do 14.?K transfers WITHOUT data compression!!
>I thought there were custom chips inside the STs that limit it to 19.2K??
>Then you have to a version of TOS that supports flow control, AND software
> that utilizes this speed.
>Did I hear another vicious rumor or can this really be done?
>
>Ed June

It's easy. You need to call Rsconf to reset a bit in the UCR, then you need
to reset the baud rate timer... Basically, when you use Rsconf to set the
baud rate of the serial port, it always puts the UART in divide-by-4 mode.
Reset that to divide-by-1, then you need to set the correct counter values
in the timer (TImer D, is it? I've forgotten already. Sigh.) to get the
baud rate you want. You can calculate them pretty easily, or, if you have
the ST Internals book, you can find the ROM values in the BIOS listing.
Multiply those by 4 for speeds in the usual range. Divide the value for 19.2
by 2 to get 38.4. It works. 61.4 can also work, but you can't do a lot of
extra processing if you want to keep up.
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