From: "da Silva, Joe" 

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Ah, I see ... if the program doesn't support higher baud rates
_and_ it uses Int 14h to set the baud rate, X00 can provide
other options without the program's knowledge. Gotcha!

Joe.

> -----Original Message-----
> From:	shadow{at}shadowgard.com [SMTP:shadow{at}shadowgard.com]
> Sent:	Wednesday, February 18, 2004 6:03 PM
> To:	opendos{at}delorie.com
> Subject:	RE: X00 and other stuff, com speed with m$dos 6.22
> 
> On 18 Feb 2004 at 13:10, da Silva, Joe wrote:
> 
> > 
> > Hmmm ... If the program _doesn't_ mess around with the 
> > UART registers, it _can't_ use anything higher than 19k2. 
> 
> Sure it can. If it uses the INT 14 calls to set the baud rate and to 
> send bytes toand receive bytes from the serial port, then it will not 
> *know* what rate the UART is actually running at. 
> 
> The *program* can think it's running at 19.2k. But X00 can run it at 
> any rate it feels like.
> 
> Also, if you've got source or can find where the baud rate divisors 
> are stored in a program, you can make a program that directly 
> accesses UART registers work at higher baud rates. A common move was 
> to replace the values for rates below 300 with those for rates 
> *above* 19.2k
> 
> 
> --
> Leonard Erickson (aka shadow)
> shadow at krypton dot rain dot com
> 

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RE: X00 and other stuff, com speed with m$dos 6.22



Ah, I see ... if the program doesn't support
higher baud rates
_and_ it uses Int 14h to set the baud rate, X00
can provide
other options without the program's knowledge.
Gotcha!


Joe.


-----Original
Message-----
From:  
shadow{at}shadowgard.com
[SMTP:shadow{at}shadowgard.com]
Sent:  
Wednesday, February 18, 2004 6:03
PM
To:    
opendos{at}delorie.com
Subject:       
RE: X00 and other stuff, com
speed with m$dos 6.22


On 18 Feb 2004 at 13:10,
da Silva, Joe wrote:


> 
> Hmmm ... If
the program _doesn't_ mess around with the 
> UART
registers, it _can't_ use anything higher than 19k2. 


Sure it can. If it uses
the INT 14 calls to set the baud rate and to 
send bytes toand
receive bytes from the serial port, then it will not 
*know* what rate the
UART is actually running at. 


The *program* can think
it's running at 19.2k. But X00 can run it at 
any rate it feels
like.


Also, if you've got
source or can find where the baud rate divisors 
are stored in a
program, you can make a program that directly 
accesses UART registers
work at higher baud rates. A common move was 
to replace the values
for rates below 300 with those for rates 
*above* 19.2k



--
Leonard Erickson (aka
shadow)
shadow at krypton dot
rain dot com




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