Mail Archives: opendos/2004/02/18/17:49:32
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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 DOT com [SMTP:shadow AT shadowgard DOT com]
> Sent: Wednesday, February 18, 2004 6:03 PM
> To: opendos AT delorie DOT com
> Subject: RE: X00 and other stuff, com speed with m$dos 6.22
>
> On 18 Feb 2004 at 13:10, da Silva, Joe wrote:
>
> >
> > Hmmm ... If the program _doesn't_ mess around with the
> > UART registers, it _can't_ use anything higher than 19k2.
>
> Sure it can. If it uses the INT 14 calls to set the baud rate and to
> send bytes toand receive bytes from the serial port, then it will not
> *know* what rate the UART is actually running at.
>
> The *program* can think it's running at 19.2k. But X00 can run it at
> any rate it feels like.
>
> Also, if you've got source or can find where the baud rate divisors
> are stored in a program, you can make a program that directly
> accesses UART registers work at higher baud rates. A common move was
> to replace the values for rates below 300 with those for rates
> *above* 19.2k
>
>
> --
> Leonard Erickson (aka shadow)
> shadow at krypton dot rain dot com
>
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<TITLE>RE: X00 and other stuff, com speed with m$dos 6.22</TITLE>
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<P><FONT COLOR=3D"#0000FF" SIZE=3D2 FACE=3D"Arial">Ah, I see ... if the =
program doesn't support higher baud rates</FONT>
<BR><FONT COLOR=3D"#0000FF" SIZE=3D2 FACE=3D"Arial">_and_ it uses Int =
14h to set the baud rate, X00 can provide</FONT>
<BR><FONT COLOR=3D"#0000FF" SIZE=3D2 FACE=3D"Arial">other options =
without the program's knowledge. Gotcha!</FONT>
</P>
<P><FONT COLOR=3D"#0000FF" SIZE=3D2 FACE=3D"Arial">Joe.</FONT>
</P>
<UL>
<P><FONT SIZE=3D1 FACE=3D"Arial">-----Original Message-----</FONT>
<BR><B><FONT SIZE=3D1 FACE=3D"Arial">From: </FONT></B> <FONT =
SIZE=3D1 FACE=3D"Arial">shadow AT shadowgard DOT com =
[SMTP:shadow AT shadowgard DOT com]</FONT>
<BR><B><FONT SIZE=3D1 FACE=3D"Arial">Sent: </FONT></B> <FONT =
SIZE=3D1 FACE=3D"Arial">Wednesday, February 18, 2004 6:03 PM</FONT>
<BR><B><FONT SIZE=3D1 =
FACE=3D"Arial">To: </FONT></B> <FONT SIZE=3D1 =
FACE=3D"Arial">opendos AT delorie DOT com</FONT>
<BR><B><FONT SIZE=3D1 =
FACE=3D"Arial">Subject: </FONT>=
</B> <FONT SIZE=3D1 FACE=3D"Arial">RE: X00 and other stuff, com speed =
with m$dos 6.22</FONT>
</P>
<P><FONT SIZE=3D2 FACE=3D"Arial">On 18 Feb 2004 at 13:10, da Silva, Joe =
wrote:</FONT>
</P>
<P><FONT SIZE=3D2 FACE=3D"Arial">> </FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">> Hmmm ... If the program =
_doesn't_ mess around with the </FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">> UART registers, it _can't_ use =
anything higher than 19k2. </FONT>
</P>
<P><FONT SIZE=3D2 FACE=3D"Arial">Sure it can. If it uses the INT 14 =
calls to set the baud rate and to </FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">send bytes toand receive bytes from =
the serial port, then it will not </FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">*know* what rate the UART is actually =
running at. </FONT>
</P>
<P><FONT SIZE=3D2 FACE=3D"Arial">The *program* can think it's running =
at 19.2k. But X00 can run it at </FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">any rate it feels like.</FONT>
</P>
<P><FONT SIZE=3D2 FACE=3D"Arial">Also, if you've got source or can find =
where the baud rate divisors </FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">are stored in a program, you can make =
a program that directly </FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">accesses UART registers work at =
higher baud rates. A common move was </FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">to replace the values for rates below =
300 with those for rates </FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">*above* 19.2k</FONT>
</P>
<BR>
<P><FONT SIZE=3D2 FACE=3D"Arial">--</FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">Leonard Erickson (aka shadow)</FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">shadow at krypton dot rain dot =
com</FONT>
</P>
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