Finding a Serial Port I/O Address Using Debug

Last reviewed: September 16, 1996
Article ID: Q78604

The information in this article applies to:

Microsoft Mouse Driver for MS-DOS, versions 6.x, 7.x, 8.x, and 9.0

SUMMARY

A serial port's I/O address can be determined with Debug.

This information applies to all serial versions of the Microsoft Mouse for MS-DOS based systems.

MORE INFORMATION

To determine a the I/O address for a serial port, do the following:

At the MS-DOS command prompt, type "debug" (without the quotation marks). (It may be necessary to change to the DOS directory for this command to work.) The debug cursor (a hyphen) is displayed.
At the debug prompt, type the following 10 characters:
```
      D 40:00 09
```
A single line of text appears, and the debug prompt is again displayed. The screen now resembles the following:
```
      C:\DOS>debug
      -D 40:00 09
      0040:0000  F8 03 F8 02 00 00 00 00-78 03
      -
```
Press Q, then press ENTER to quit Debug.

The line of interest begins 0040:0000. In this example, the F8 03 and F8 02 indicate two serial ports (COM1 and COM2). Other possibilities include E8 03 (COM3) and E802 (COM4).

A machine with four serial ports should read as follows:

   0040:0000  F8 03 F8 02 E8 03 E8 02-78 03

A machine with no serial ports should read as follows:

   0040:0000  00 00 00 00 00 00 00 00-78 03

A machine with two serial ports (COM2 and COM3) should read as follows:

   0040:0000  F8 02 E8 03 00 00 00 00-78 03

The -78 03 in the above example is the address of the first parallel port.

Note: Windows only recognizes the Mouse on COM1 or COM2. Portables may need their serial ports enabled before the system can recognize them as serial ports.

KBCategory: kbhw
KBSubcategory:
Additional reference words: com communications input output
BallPoint

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Last reviewed: September 16, 1996
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