The below debug routine will check the ports of the computer to allow you to know if ports are being detected or not.

Type debug to get to the “-”

Type D40:0

You should get several lines; however, the first line is the only important line, which should read the following:

0040:0000 F8 03 F8 02 E8 03 E8 02 – 78 03 78 02 BC 03

F8 03

F8 02

E8 03

E8 02

78 03

78 02

BC 03


The above graph shows you what the feed back means as far as port, so if you see F8 03, this would be an indication that COM1 is being detected; if you see 00 00, this is an indication that it is not being detected, which could mean that hardware is bad or that it is disabled in CMOS.

Once you have finished looking at the information, type Q and press enter to get out of Debug.