Maximum baud rate of dev-ser8250

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Alex B.

Maximum baud rate of dev-ser8250

Post by Alex B. » Fri Nov 21, 2003 1:09 am

Hello, - I am looking for info on dev-ser8250, in particular the maximum
baud rate supported by the driver. The only mention I found in the
documentation is the default 57600 bps. My serial card supports up to
921.2kbps, but so far I could only get it up to 115200.
Thanks.

Bill Caroselli

Re: Maximum baud rate of dev-ser8250

Post by Bill Caroselli » Fri Nov 21, 2003 12:57 pm

Alex B. <alexbabinski@msn.com> wrote:
AB > Hello, - I am looking for info on dev-ser8250, in particular the maximum
AB > baud rate supported by the driver. The only mention I found in the
AB > documentation is the default 57600 bps. My serial card supports up to
AB > 921.2kbps, but so far I could only get it up to 115200.
AB > Thanks.

I believe that that is the fastest that you can set with dev-ser8250.
To achieve a higher speed the device must have it's own driver.

Guest

Re: Maximum baud rate of dev-ser8250

Post by Guest » Tue Nov 25, 2003 8:14 am

Bill Caroselli <qtps@earthlink.net> wrote:
Alex B. <alexbabinski@msn.com> wrote:
AB > Hello, - I am looking for info on dev-ser8250, in particular the maximum
AB > baud rate supported by the driver. The only mention I found in the
AB > documentation is the default 57600 bps. My serial card supports up to
AB > 921.2kbps, but so far I could only get it up to 115200.
AB > Thanks.

I believe that that is the fastest that you can set with dev-ser8250.
To achieve a higher speed the device must have it's own driver.
Some cards have jumpers, that act as baudrate multipliers. So the software thinks
it is running at 115200 while in fact it is doing 921.2. I have no experience
with really running that high baudrates though.


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Horst Hannappel

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ed1k

Re: Maximum baud rate of dev-ser8250

Post by ed1k » Tue Dec 09, 2003 12:52 am

In article <bpjnh7$mdt$1@inn.qnx.com>, alexbabinski@msn.com says...
Hello, - I am looking for info on dev-ser8250, in particular the maximum
baud rate supported by the driver. The only mention I found in the
documentation is the default 57600 bps. My serial card supports up to
921.2kbps, but so far I could only get it up to 115200.
Thanks.
'use devc-ser8250' should give you a hint, particularly option '-c clk/[div]'. Actual divider which
is written to "divider latch registers" is calculated as
clk/(baud*div), where clk=1843200 and div=16 by default.
I suppose you have to consult manual for your board and play around clk/div parameters.
BTW, did you measure actual baud rate or do you assume the baud rate is 115200 because 'stty'
utility reports it? 'stty' will be fooled if crystal on your board is different than standard and
you don't use -c option.

Eduard.

John Nagle

Re: Maximum baud rate of dev-ser8250

Post by John Nagle » Thu Jan 01, 2004 10:13 pm

With dev-ser8250, you'll take an interrupt at least once every
16 bytes, even if it works. The interrupt load is huge,
and you may get data overruns.

Our (painful) experience with high-speed serial is that
something like the Sealevel Ultra 4103 Ethernet to serial
converter is the way to go. That will actually go to about
900Kb/sec.

John Nagle


Alex B. wrote:
Hello, - I am looking for info on dev-ser8250, in particular the maximum
baud rate supported by the driver. The only mention I found in the
documentation is the default 57600 bps. My serial card supports up to
921.2kbps, but so far I could only get it up to 115200.
Thanks.

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