X1541TST.ZIP            X1541 Test, version 0.10                  1999-01-12

(C) Copyright 1999 Wolfgang Moser, published under the GNU public license


1. Introduction

This is X1541TST, a program written for testing the LPT ports of IBM
compatible PCs regarding their compatibility with the X1541 cable. It needs
the assistance of a simple loopback plug that has to be connected to the LPT
port of interest.

This document is not intended as a tutorial about the technical background
of the different transfer cables and the different types of LPT ports,
please read the file SC.TXT that comes with the Star Commander if you're
interested in these topics.

2. Hardware

The loopback plug needed for this program can be made as easy as bending
open a paper clip or it can be built into its own plug with case. Both
versions will be described here.

Here is the pinout of the LPT port, it is shown in a way as if you were
looking directly onto your printer port at the back of your PC. The same
pinout applies if you look at the back side (solder side) of a male DB-25
connector which you need to make a real loopback plug. On most connectors
the pin numbers are actually printed in small letters beside each pin or
hole.



            PaperEnd   Busy
        SelectIn         Ack        Data 7 - Data 0       Strobe
                           Ŀ   
               V   V   V   V                                 V
            ͻ
             13  12  11  10   9   8   7   6   5   4   3   2   1   
              o   o   o   o   o   o   o   o   o   o   o   o   o   
            ͻ                                                  ͼ
                o   o   o   o   o   o   o   o   o   o   o   o   
               25  24  23  22  21  20  19  18  17  16  15  14   
              ͼ
                                               ^   ^   ^   ^
                             
                            Ground          Select         AutoFeed
                                                  Init   Error

The paper clip method

First, be warned that this method is not advised by us and that you do this
on your own risk. We will not be responsible for any damage that might
happen to your equipment. But, of course, this method was tested and never
caused any damage to our equipment.

Now take a paper clip from your desk and bend it open until it looks like a
tall, narrow U shaped piece of wire. The two ends will be plugged into pins
1 and 14 of the LPT port. If you look at the port in a way as shown in the
diagram above, these will be the rightmost holes of both the upper and lower
row of holes. When the program asks you to insert the loopback plug, insert
the paperclip into the holes described above. That's it, nothing more is
needed to make the program work. Don't forget to remove the paper clip when
you're done with testing.

LPT port pins                  paper clip (bent open)

      1                            -------------\
                                                 |
      14                           -------------/



The better way to do it

The paper clip method is quick and easy, but there is always a danger of
inserting the clip into the wrong holes and this might cause trouble. Also
the clip has a resistance of only about 0 Ohm, which may cause trouble on
certain types of printer ports. Therefore a device will be described here
that is better suited for repeated use, because it can't be plugged in in a
wrong way, also resistors instead of simple wires are used to provide a
means of protection against short circuits.

You need a male DB-25 plug and a case for it, you also need two resistors in
the range of 220 Ohm to 1 kOhm. You shouldn't take resistors outside this
range. You also need a soldering iron to connect the resistors to the plug
and perhaps a screwdriver to assemble the case and the plug.

One of the resistors is connected to pins 1 and 14 of the plug, the same
pins that are used for the paper clip method. The other resistor connects to
pins 16 and 17 of the plug. This additional connection makes the test more
reliable than with only one connection. The program will report how many
working connections it found on the plug. So be alerted if you know you made
a plug with two connections, but the program reports only one of them.


male DB-25 pins                      resistors

      1                            -----/////---\
                                                 |
      14                           -------------/

      16                           -----/////---\
                                                 |
      17                           -------------/


3. Software

The X1541TST program is invoked from a DOS or Windows (3.x/95/98) DOS box
command line. It will not work under Windows NT, but it will probably work
under OS/2 and Linux Dosemu. Just type X1541TST, the program will then
prompt you to install the loopback plug. After doing so, the program will do
the test and report the X1541 compatibility as a result. Also reported is
the type of your LPT port and some hints which additional cables you can
connect to the same port. There are command line options to make the program
give more hints about possible cable combinations. You can get help on these
options by typing X1541TST /? at the command prompt.

4. Copyright and legal issues

This program is provided "as is", without a warranty of any kind. You are
using it at your own risk. The author is not liable for any damage or data
loss caused by the program.

5. Contacting the author

Wolfgang Moser can be reached by email <womo@mindless.com> or visit his
homepage at http://www.gm.fh-koeln.de/~womo

This document was written by Nicolas Welte, email
<welte@chemie.uni-konstanz.de>
