HP-IL Printer (odd?) page shifting when disabled.

[Diego Diaz]

Hi J-F,

Sorry, I may have misled you by (wrongly) referring to the A9 line. It is A13 (now edited) the line that is switched.

I missed a whole nibble when counting from the top of my head... this wouldn't have happened 20 years ago. I'm not getting younger.

A13, and also A14, already have their own pads on the 40K ROM die so no need to further design, added pad or new chip mask.

On a Standard ROM A15 is masked to 1 to trigger the CS/ signal. While A14 and A13 are port dependent and connected to B4 & B3 lines, respectively. B4 & B3 lines were named after the original 16 register D/S chip pads, as they served essentially the same function for the 82106A modules.

On HW addressed ROM's (TIMER, PRINTER, HP-IL, DIAG...) A15 is masked to 0, and A14-13 wired to match desired for that specific ROM.

I didn't think of the TEST pad though, good point. It would indeed be a reasonable alternative.

Again, maybe we will never know... :-)

Cheers

Diego.