A4000 mystery header - how to read it?

[ali1234]

I quote Dave Haynie:

There is a 12 pin header (DIL, J975) near the mouse ports. This feeds the   'extra' shift register in Lisa. Unlike OCS/ECS systems, which simply   multiplex the four quadrature signals from each mouse port with one   another, the AA systems serialize all eight bits of mouse data. While they   were at it, the AA designers added a second 8-bits to the mouse port   registers. These don't hook into mouse logic or anything, but they can be   read by the CPU.

So, does anyone know how to read the values? Can the other shift register be directly read also?

[ali1234]

The second shift register data can be read from high byte of LISAID. The Non-jumpered bits will read as 1, and if you jumper them they will read as 0. The two lowest bits are hardwired to ground and read as 0, so by default the register will read as 11111100 (252 decimal).

This is the opposite of what you get from the JOYxDAT registers, which read a 1 when the line is pulled to ground.

Code: [Select]

#include <exec/types.h>
#include <stdio.h>

#define LISAID  (*(UWORD *)0xDFF07C)

int main(int argc, char *argv[]) {
    printf(&quot;%d\n&quot;, LISAID>>8);
    return 0;
}

This won't work in uae.