Dec 272017
Use IBM's serial port as COM3.
File COMM3.ZIP from The Programmer’s Corner in
Category Communications
Use IBM’s serial port as COM3.
File Name File Size Zip Size Zip Type
ASYNC3.SYS 2375 1343 deflated
COMM3.DOC 1348 768 deflated
TERM.EXE 16800 7939 deflated

Download File COMM3.ZIP Here

Contents of the COMM3.DOC file

The purpose of this program is to allow the addition of an extra communications
port to IBM-family machines. This is a programmable port addressed as com3: andlocated at address 3e8h. It may be configured
using the TERM.EXE program. Type TERM HELP for details.

The existing IBM-supplied single communications port may be used in this application if installed multi-function boards are
presently supplying COM1: and COM2:

1.Break trace A27 to U2-5
2.Connect A27 to U6-12
3.Connect U6-11 to U2-5
4.Connect U6-13 to +5Vdc. (U6-14)
5.Break trace from U15-6 to B25
6.Connect U15-6 to B4.

Refer to IBM Technical Reference Personal Computer XT for above designations.

These wiring changes should only be undertaken by personnel experienced and
equipped with PC board tools and the techniques involved.

Install async3.sys in the config.sys file as DEVICE=ASYNC3.SYS
The new serial port will not appear in the port table located at Segment40:0

This modification may be used with any software that allows you to specify either COM3: or port 3E8h.

Direct inquiries to:
Art Shulman,
Box 850
Waterford, Ontario, Canada.
N0E 1Y0

Telephone (519) 443-4321 after 6:00 Pm. EST.

Files included: This file you are reading.


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