06-04-2013, 04:35 AM
It was JF Garnier who pointet me to the fact, that during the {ON + *} test of the HP-15C the 'display registers' of the second R2D2 chip afford a correction as the read value from these registers differs from the written. The six LSB are unused.
But it looks to me, as if the returned value from these unused bits once are all 1's or all 0's, depending what was written before. I can hardly believe that. But as I have no chance to program the 15C in MCode I may only guess what realy happens. Someone here may shed some light to it please?
TIA.....Mike