Description: Apple II Hardware: The Apple II Keyboard
Header: Apple II Hardware: The Apple II Keyboard

 The keyboard on the Apple II has an upper-case-only encoder.  It can produce
 ASCII characters 0 through 95, excluding _ , \ , [ , CTRL-_ , CTRL-[, and
 CTRL-\.  The Apple III uses the very same encoder.  However, the Apple III
 also has a second keyboard port; with this port, the Apple III can
 independently to sense the shift, control, and alpha lock keys, as well as a
 number of other functions.

 You can modify an existing Apple II to allow it to sense whether or not the
 shift keys are depressed.  This modification is supported by system software
 such as Pascal 1.1 and Pilot, as well as some word processing software.  The
 core of the modification is a wire running from the shift keys to button input
 2 of the game I/O port which button input the paddles don't use.  This
 modification is not recommended for in-warranty Apples and should be only
 performed by an authorized service technician.

 Since the modified Apple can sense whether or not the shift key is being
 pressed, it can distinguish 51 new characters: CTRL-SHIFT-A thru Z excluding
 M, N, and P, SHIFT-A thru Z excluding M, N, and P, SHIFT-0, SHIFT-RETURN,
 SHIFT-ESC, SHIFT-LEFT ARROW, and SHIFT-RIGHT ARROW.  This raises the total
 number of distinguishable characters to 141, which easily encompasses the 128
 member ASCII character set.

 To facilitate the most natural use of the keyboard, software sometimes
 rearranges the interpretation of these characters so that the keyboard
 resembles that of a typewriter. Apple has employed several types of keyboards
 on the Apple II since its introduction, so the modification has two
 appearances.

 1. On the older style keyboard, a wire should be run between pin 2 of the
   74LS00 and pin 4 of the keyboard connector on the keyboard.

 2. On the newer style keyboard with the "piggy-back" electronic assembly, the
   wire should be run between pin 9 of the 74LS00 closest to the keyboard
   connector and pin 4 of the keyboard connector.

 In either case, a second wire should connect the bottom of pin 4 at location
 A7 to pin 7 at location J14 on the motherboard. Check carefully that the wire
 isn't connected to pin 7 of H14. The keyboard cable acts as a connection
 between these two wires.
 Apple Tech Notes


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