One of the things I had been lamenting was that the apple II+ keyboard couldn't type all of the characters. Turns out there was a cool device called the Videx Enhancer II that would do this, and in addition, also provide macro keys. There was also a function key strip that would plug into it called the Videx FunctionStrip.
This board would install in between the keyboard and the apple ii.
It had a 6502 processor on board with 1k of memory to monitor the apple 2 keyboard and pass the keystrokes along.
It's cool that there was great documentation providing full source code and schematics.
I wanted to look at the code and figured out by pausing the apple II driver, I could load the rom file into memory at $1800 and use the mame debugger to do the disassembly.
load "Videx Enhancer II ROM - 2716.BIN",1800
The rom file doesn't exactly match up with the assembly listing given in the manual, but it's pretty close.
The following are some of the Enhancer ]['s features:
*Full ASCII keyboard (128 ASCII codes)
*The complete printable ASCII character set —including lower case — may be displayed
*User definable keys — with down loading from disc [section: 5.f]
*Type ahead buffer [section: 5.g]*Auto repeat [section: 5.a.3]
*Fast repeat [section: 5.a.3]
*Normal Apple ][ mode [section: 5.d]
*Typewriter like operation [section: 5.e]
*Shift—lock feature [section: 5.e.1]
*Control — Reset protection (section: 5.c.1]
*Simple installation [chapter two]
*Microprocessor controlled (6500 series)
*Self test diagnostics [section: 5.h]
*A 2716 EPROM is used for on board firmware
*Complete firmware listings [appendix Y]
*Complete schematic [appendix Z]
*Dvorak keyboard option
Your new keyboard Enhancer ][ utilizes a sophisticated microprocessor with its own RAM. Although the Enhancer ][ is more sophisticated than it’s predecessor, the Keyboard & Display Enhancer, it is significantly easier to install. The microprocessor extends the features of the Enhancer ][ beyond those of the original Keyboard & Display Enhancer with features such as user definable keys and a type ahead buffer. The caps lock, caps unlock, shift lock and control — reset features are preserved, thus supporting the normal Apple ][ keyboard as well as a typewriter like mode.
Ul—2716 EFROM (Enhancer ][ Firmware)
U2—6504 Microprocessor (6502 instruction set)
U3—2114 1K x 4 RAM
U4—2114 1K x 4 RAM
U5—74LS05Hex inverter, open collector
U6—74LS373Octal D latch
U7—74LS139Dual 2—4 line decoder
U8—74LS05Hex inverter, open collector
U9—74LS373Octal D latch
U10—74LS374Octal D flip—flop
2N3904 — Reset logic