Bryan Parkoff wrote:
The IIe has moved the keyboard encoder chip off the keyboard PCB and onto the motherboard. The keyboard connector on the IIe takes an un- encoded X-Y matrix of SPST switches and has 26 pins (18 pins for the 8x10 matrix, 6 pins for PB0 PB1 CAPS SHIFT CTRL & RESET and 2 pins for +5V and Gnd).Do you think that PS/2 keyboard will work unless you build small PCB? The PS/2 keyboard's signal will go to the small PCB with few chips. Then it will be translated to Apple II & //e's encoded ASCII matrix.
Not a good idea building a board to produce the "matrix" signals. Way too complicated.
Just pull out the "keyboard ROM" (E12) chip and plug the PIC based circuit in. The output of the "keyboard ROM" is the keyboard data, largely the same as in 2/plus.
One would need a tri-state buffer like 74HC244 controlled by ENKBD' that is connected to CE' of the keyboard ROM chip.The RESET on the original keyboard will still work. Even if the keyboard encoder chip is also pulled.
An alternative solution is to keep the "keyboard ROM" in place, but pull the keyboard encoder chip and reprogram the PIC to generate whatever codes are produced by the encoder chip. This would be a single (PIC) chip solution.
-Alex.