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Cannot connect over 9600 bps on any COM port using any modem !!

Posted on 1997-06-13
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Last Modified: 2013-12-16
I have a US Robotics 33.6 v.Everything PCMCIA modem (on COM4) that I can connect to ANY other modem at only 9600 bps.  I have tried an external USR Sportster 28k on COM2 and had the same results.  I have tried ALL the "Maximum Speed" settings in the modem properties, with & without Hardware Flow Control.

My communications driver is comm.drv  5856 bytes  dated: 7/11/1995 09:50am.

I have also tried the Modem device via the Device Manager in the System icon in the Control Panel... no luck.

Are there any useful shareware diagnostic utilities that could shed some light on this problem?  Any ideas would be appreciated.

Please reply to:  hooligan@usa.net

Thanks!

hooligan@usa.net
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Question by:lebaron
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smeebud earned 100 total points
ID: 1748798
I assume you do have a 16550 UART CHIP. Check MSD to see what the UART  is. Sometimes systems somehow forget this or it GOES BAD. I've had it happen with the same symtoms as yours.
Other-wise, check your advanced port settings in "device manager" to see if your uart is correct.
Or go to USR home page, they have diags there.
http://www.usr.com/
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by:smeebud
ID: 1748800
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by:smeebud
ID: 1748801
Diagnostic you say:
http://www.dlr.de/fresh/pc/src/misc/.warix/ctsspu22.zip.html
ctsspu22.zip - COM port & modem setup & diagnostic utilities
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Expert Comment

by:LouA
ID: 1748802
What IRQ are you set-up on?  Did you go in the Device Manager and try and change the configuration, since you did change to use COM 4.  Most modems use COM 2.  Is the modem set up at its MAX speed, use 57600. Check in Properties, port settings, is the box for "use FIFO buffers (requires 16550 compatible UART)" checked. Still in properties, click advanced  the following should be checked "Use error control, Use flow control, compress data and the radio dial for Hardware(RTS/CTS) also checked (dot). Modulation type: standard.  Also check out your bias set up this should be ok, if the modem is working.  
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