Serial port speeds and Hyperterminal

Hi,

I have connected a W95 box to a XP box using hyperterminal and can
communicate and dump files from one to other (usually only one file at a
time - is it possible to send more than file using Hyperterminal??)

Its works pretty well, but can only handle up to about 110,000 bps (about
13Kps). That was setting the connection speed at 115200.

However, if I go into the properties of the serial port in Control
Panel/System/Device Manager/Ports/Serial port/Properties, I can go up to
something close to 1m bps. However, after changing this property and
retrying the connection, I always to open the COM port at speeds in excess
of 115200 bps.

Is that the absolute limit at serial connection? Is it perhaps a limitation
of Windows 95/XP or am I doing something wrong?

Thanks in advance,
Alain

Just re-reading that, I realise I've mangled the grammar, I meant to say in
the last bit, instead of this:

"...However, after changing this property and retrying the connection, I
always to open the COM port at speeds in excess of 115200 bps..."

this: "However, after changing this property and retrying the connection, I
always get an error opening the COM port at speeds in excess of 115200
bps..."

Thanks,
Alain

"Alain Dekker" wrote in message
...
| this: "However, after changing this property and retrying the connection,
I
| always get an error opening the COM port at speeds in excess of 115200
| bps..."


115,200 is the upper limit of the UART (Serial port controller) chip
(Universal Asynchronous Reciever Transmitter).
It's no surprise that you get an error at higher speeds.

Kev

Hi Kevin,

Thanks for that information. Any idea why the properties of the device
mention higher speeds, then (such as 234000+ on Win95 or 128000 on my XP
box)?

Thanks,
Alain

"Kevin M" wrote in message
igy.com...
"Alain Dekker" wrote in message
...
| this: "However, after changing this property and retrying the
connection,
I
| always get an error opening the COM port at speeds in excess of 115200
| bps..."


115,200 is the upper limit of the UART (Serial port controller) chip
(Universal Asynchronous Reciever Transmitter).
It's no surprise that you get an error at higher speeds.

Kev

"Alain Dekker" wrote in message
...
| Hi Kevin,
|
| Thanks for that information. Any idea why the properties of the device
| mention higher speeds, then (such as 234000+ on Win95 or 128000 on my XP
| box)?

The only thing I can think of is some kind of software compression algorithm
that would allow higher throughput.
I do see, in device manager, that the highest available option in XP is
128,000. This strikes me as odd. Gotta be compression.
All I know, from my DOS days, is that a 16550 UART will reach a physical max
speed of 115,200. I fought with this for some years with 16450 UARTs that
would do significantly less max throughput.
I also had a bit of a head scratcher at a customers site. They had a
PalmPilot that just would NOT synch up. Turns out the user had the serial
port speed too high for the Palm. All I had to do was to set the port back
to 9600, and voila.

HTH,
Kev

Kevin M wrote :
"Alain Dekker" wrote in message
...
| Hi Kevin,
|
| Thanks for that information. Any idea why the properties of the
device
| mention higher speeds, then (such as 234000+ on Win95 or 128000 on my
XP
| box)?

The only thing I can think of is some kind of software compression
algorithm
that would allow higher throughput.
I do see, in device manager, that the highest available option in XP is
128,000. This strikes me as odd. Gotta be compression.
All I know, from my DOS days, is that a 16550 UART will reach a
physical max
speed of 115,200. I fought with this for some years with 16450 UARTs
that
would do significantly less max throughput.

How about the original 16550's (no "A" suffix) with the broken FIFO's?
They were a pain...

There are serial devices (inc. modems) that support speeds of 230400, or
even higher. My old 33.6 modem supports 128000, and will use that
setting, with my DOS terminal program. Unfortunately, I can't make
"128000" show up as a valid setting, either in Port settings, or Modem
settings, even though I see that speed listed in both SERIALUI.DLL and
MODEMUI.DLL. Does anyone know of a way to make 128000 'visible' in Win95
original version? Did later Win95 versions support this speed?

Alan would have to check if his serial port does support speeds higher
that 115200 (it probably won't, if older; and still may not, if newer).
Also, if he has MS-DOS version 6.x, he may want to check out
INTERLNK.EXE and INTERSVR.EXE for file transfers, etc.; they're easy to
setup, use little resources, and I've found them to be very reliable.
And, the "Notes" section of INTERLNK's help has construction details for
a parallel link cable, which would be significantly faster than a serial
link.

Ken

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