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Testing a Serial Port in DOS
Yair_Churi May-23-01 02:59 AM
I have a serial port on a DOS machine (v6.22). Is there a command so that if I connect COM1 to a Hyper-Terminal I can see characters on the screen? Otherwise, how can I test that the port and the cable works?

Thank you,

1. RE: Testing a Serial Port in DOS
lbyard May-23-01 05:42 PM
In response to message 0
There may be a diagnostic program that came with the MODEM, if that is what you are connecting to. You can pretty much tell whether the serial port and cable are working or not by typing something in the Windows HyperTerminal and looking at the LEDs on the MODEM. MS Diagnostics (MSD) that comes with Windows 95 and MS-DOS 6.X is useful for determining if a serial port is responding. A loopback test, which requires a loopback plug/adapter, is a very good test of a serial port. Several commercial diagnostics programs (e.g., AMIDiag: http://www.ami.com/ami/showpress.cfm?PrID=69) come with a loopback plug. When a loopback test is run data is sent out the serial portís transmit pin to the loopback plug which sends the data back to the portís receive pin. This test assures the 1488 and 1489 buffer chips or equivalent are working and they are the chips that are usually damaged by a close lightning strike, etc. Scott Muellerís Upgrading and Repairing PCs has more info and instructions for making a loopback plug. Just search http://www.google.com for the book. Every shop should have a copy. However, the best and easiest to read shop reference on serial ports and cables I know of is Data Communications for Microcomputers by Elizabeth A. Nichols, Joseph C. Nichols, and one of my business acquaintances from the old days, Keith R. Musson, McGraw-Hill 1982. I think it is out of print. An RS-232 breakout box (http://www.bb-elec.com/product.asp?sku=232BOB1E&dept_id=136) and a multimeter are useful tools for troubleshooting serial ports and cables. I test MODEMs by dialing a local Internet Service Provider with Windows Hyperterminal (I used to dial a local bulletin board). Larry

2. RE: Testing a Serial Port in DOS
ashes May-28-01 03:58 PM
In response to message 0
Hii there
u can use MSD which is shipped along with DOS 6.22
or you can use a utility caled amidiag
alternatily u can try conecting a moedm to the com port and thry the diagnostics on that using the AT command set
this can be done from the commant prompt

eg: " echo AT&F>com1"
or any other at command
hope this was of soem use to u

3. RE: Testing a Serial Port in DOS
lbyard May-28-01 05:28 PM
In response to message 2
Yesterday, I added an FAQ on this subject at http://duxcw.com/faq/modems/modems.htm which you may find useful. Use of the AT command is a neat idea. Larry

4. testing com ports on dos
ashes May-29-01 02:29 PM
In response to message 0
hope u had success with the AT command using modem


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