Atari XL/XE function keys

The Atari 1200XL introduced four function keys.
When the original 400/800 Atari 8-bit machines were re-engineered to the ill-fated 1200XL, Atari dropped 2 joystick ports from 4 to 2, added on-board diagonstics, BASIC ROM and four function keys. Back in fall of 1984, I acquired my Atari 600XL with TRAK disk drive, joystick, and two games. Since the XL/XE Atari OS still retained code for function keys, I modded my 600, later re-adding abandoned cursor/function keys.
Extra buttons default to cursor keys, Shift to jump within page top/bottom/left margin/right margin, and Ctrl for special features. (Keyboard Lock, DMA or Screen Blank, Key Click, Ctrl Chars.)
^{Video DMA disabling elicits a CPU processing ‘speed-up’ used for faster number crunching or DSP/digital audio playback.}



My original 600XL keyboard used non-membrane keyboards before cost reductions.
first three images show keyboard traces, last shows missed 1-2” section between 1^st & 2^nd

Here is my added four Tac switches on circuit board.
Wires (right to left) are Orange-17, Yellow-10, Green-8, Blue-5
24 pin keyboard ribbon/connector, solder wires to pins 5, 8, 10, 17 from top of case.
⇧ Y-B (pins 10 & 5)
⇩ O-B (pins 17 & 5)
⇦ Y-G (pins 10 & 8)
⇨ O-G (pins 17 & 8)