TRANSFERRING DATA BETWEEN COMPUTERS
by Clarence Heier
Transferring files and programs among the various
formats is perhaps a more significant problem with
the Micro Decision than with other computers
because of the relatively recent arrival of the
Morrow format. Software is becoming more
available in the MD format and the fact that
Osborne and Xerox formats can be read is an
advantage. There are many occasions when it is
desirable to be able to transfer data from an 8"
system to the Morrow format. This can easily be
done via modem, but the time involved is
significant especially at 300 baud. This transfer
can more quickly be accomplished if the two
computers are in close proximity to one another.
The communication program Modem 7 (or any others
that use the Christensen protocol) can serve as
the software to allow the transfer at speeds up to
19,200 baud (9600 baud for the MD2). All that's
necessary is a specially-prepared cable to connect
the two computers via RS232 ports, no modem
required.
To prepare the cable, look at the diagrams below.
It is advantageous to have both cables prepared as
outlined. Also, it would behoove you to have a
male-female and a female-male gender adapter
handy. Armed with these cables, your Modem
program, your computer and the software you want
to trade, you can swap with any other CP/M user.
The only thing required of the other party is a
communication program compatible with yours. Even
this program can be transferred to him from your
system, but some modifications to your PIP program
will be necessary, or you must have the hex file
of your modem program.
To prepare the cables follow these two diagrams.
Make the straight through cable fairly long with a
male RS232C connector on each end. Make the
crossed cable shorter and put a male connector on
one end and a female connector on the other end.
Straight-Through Cable Crossed Cable
(Pins 2 & 3 crossed)
----------------------- ---------------------
End End End End
A to B A to B
Pin Pin Pin Pin
2 ----------------- 2 2 ------+ +---- 2
+-|---+
3 ----------------- 3 3 ----+ +-------- 3
7 ----------------- 7 7 --------------- 7
4 --+ +-- 4 4 --+ +-- 4
5 --+ +-- 5 5 --+ +-- 5
6 --+ +-- 6 6 --+ +-- 6
8 --+ +-- 8 8 --+ +-- 8
20 --+ +-- 20 20 --+ +-- 20
To use just hook the computers together as if the
other computer is a modem. The crossed cable will
probably be required, unless the crossing is done
within either of the computers. Experiment until
you get both computers talking to one another in
terminal mode. Then simply transfer files as you
would if you were on the phone. Make sure that
both computers are running at the same baud rate.
Transfer time at 9600 baud is 32 times faster than
at 300 baud. A full disk can be transferred in
minutes instead of hours. Try it and let me know
of any problems you run into.