Path: utzoo!censor!geac!torsqnt!hybrid!scifi!bywater!uunet!cpqhou!randys
From: randys@cpqhou.uucp (Randy Spurlock)
Newsgroups: comp.os.msdos.programmer
Subject: Re: Setting BAUD rate with MODE command
Message-ID: <1991Jan09.150149.15065@cpqhou.uucp>
Date: 9 Jan 91 15:01:49 GMT
References: <1991Jan9.003303.18953@thyme.jpl.nasa.gov>
Distribution: na
Organization: Compaq Computer Corporation
Lines: 45

in article <1991Jan9.003303.18953@thyme.jpl.nasa.gov>, kaleb@thyme.jpl.nasa.gov (Kaleb Keithley) says:
> 
>>
>> ***** Real message deleted *****
>>
> 
> If you RTFM, the one you got when you bought DOS.... you did buy it didn't
> you?  You will see that 19200 is indeed invalid.
> 
> That's because if you look at how mode is implemented, i.e. braindead....
> oops, I mean with a BIOS function call, and how the BIOS is implemented, 
> packing all the parameters into a register, such that the value derived 
> for 19200 is larger than will fit into the bits allocated for the baud, 
> you will see that 19200 is indeed an invalid baud rate.
> 
> Now, since you're looking at the BIOS listings to see this, you can 
> plagarize your own version of mode that doesn't try and pack baud, parity, 
> and stop bits into one sixteen bit register, and therefore skirt the bogus
> baud rate warning.
> 
> Have fun.
> -- 
> Kaleb Keithley                      Jet Propulsion Labs
> kaleb@thyme.jpl.nasa.gov
> 
> Offensive quote coming soon to a .signature file near you.

I hate to be picky, but since I developed the mode command for MS-DOS 3.0
and programmed BIOS ROM's, I have to take offense! If you would read the
data sheet for the Intel 8250, the original asynch. chip used in PC's, you
would have seen that the data sheet said the baud rate generator was only
good up to 9600 baud, even though you could program it up to 115.2 Kbaud,
and my experience is that 19.2 Kbaud works on every machine I have tried.
But to be fair to us "brain-dead" BIOS coders we simply followed the data
sheet recommendations and only supported up to 9600 baud :)!


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          - Randy Spurlock -	      |      Compaq Computer Corporation    
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These opinions are mine...all mine... | He fired his hyper-jets and...  
just ask anyone who's heard them!     | blasted into the 5th dimension!
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UUCP: ...!uunet!cpqhou!randys         |                     Space Man Spiff
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