Date: Wed, 15-Aug-84 22:33:00 EDT
Posted: Wed Aug 15 22:33:00 1984
Date-Received: Sun, 19-Aug-84 01:40:55 EDT
To the AppleUsers^.es dl:
A question was raised by someone on the info-apple at Arpa (and
alternately the XeroxInfo-Apple^.pa dl). The question brought this
response from me. Since I thought it may be useful information to those
of you that are not on those dl's I've decided to "fill you guys in".
The question was:
" . . . could someone describe the modification to the Apple ][+
keyboard that enables transmission of both upper and lower case ? I
have heard that it is a simple one wire mod."
The one wire added is the signal line of the actual SHIFT key to pin 4
of the "Game I/O" (the 16 pin socket that the paddles plug into). Pin 4
is a typically unused pin of the Game I/O, but if you look it up there
is an input designated for it. That input is PushButton 2 (PB2).
Almost everybody has no need for PB2, (PB0 and PB1 are the ones used on
the paddles or joysticks). Knowing that, somebody (not of Apple, but of
some software manufacturer) decided to provide some nice feature there,
the "one wire shift mod".
If you have the newer 2 piece keyboard (also called the "piggyback
keyboard) identifiable by the small board hanging under the keyboard,
and connected to the keyboard by 25 in-line pins (each pin is about 1"
long) then the SHIFT signal you want is actually pin 24 of that 25 pin
If you have the old one piece keyboard, where all of the keyboard keys
and the encoder chip and some other chips are all located on the same
board, then you will have to locate the SHIFT line yourself.
Whatever; once you find that SHIFT signal (its normally high [about 5
volts] until you press SHIFT, then it is held to ground [0 volts]) you
then wire it to pin 4 of the Game I/O. If you use a wire with clips on
the ends you will then be able to easily remove it if you ever have to.
HOW THE DARN THING GIVES LOWERCASE
All this one wire shift mod does is give a signal to the pin 4 of the
Game I/O which indicates if the SHIFT key is being pressed. The one
wire shift mod does not give lowercase. It is up to software (or
firmware) running in the Apple to recognize that SHIFT signal and
properly interpret (or re-interpret) the real keyboard UPPERCASE
characters into the desired lowercase characters.
Now that that is out of the way. You might like to know that all is not
bleak, many of the newer software packages that have any need for you
to ever enter lowecase characters (word processors come to mind, mainly)
have the proper coding to continually read that pin 4 of the Game I/O,
whether or not you have the one wire shift mod in. That way, if you do,
the keyboard will be re-interpretted otherwise the keyboard will be read
Lastly, this "one wire shift mod" will work on any Apple. Generally,
there is no need for it in the Apple IIe or the Apple IIc, since both of
them have real UPPER/lowercase keyboards. But, there is always the
exception! Some software running on any kind of an Apple can make use
of the additional information of whether or not you are pressing the
SHIFT key, regardless of the kind of Apple you have. For example
normally there is no difference between a ctrl-q and a ctrl-Q. Both
send the same ASCII code to the Apple motherboard, BUT with the "one
wire shift mod" you can now recognize (if you have software reading PB2)
the difference and handle them in different ways. This gives you about
another 26 new control character possibilities! (there are 26 letters in
the alphabet but there are 32 control codes AND BUT some of the
characters won't be available).
(Note: The Apple IIe rev. A and rev. B motherboards have another
difference! One of them, and I'm not sure which, has the "one wire
shift mod" already wired in. There are other differences too, but
that's one you might not have known about.)