Processor Instruction Sets

[Alejandro Paz(Germany)]

Regarding P on the woodstocks, I recently thought that maybe it wraps from 13 to 0 and from 0 down to 13 and that causes the problem, what may have been a good idea to avoid 14 and 15 may have caused more problems. (Haven't tested this idea).

What baffles me is the apparent random choice of opcodes, arguments and encoding of the arithmetic group. I suppose they where implemented in a kind of PLA (hardwired) where it didn't make any difference to sort them or not. Maybe the circuits in the patent can shine some light, but I did not want to look into them and "taint" my efforts .

Regarding the encoding of literals, maybe they where trying to obfuscate it in case the people at ti wanted to copy it ? Anyways ti approach is a bit different, if I remember correctly. (At least the TI-81..6 have no special purpose processor but uses Z80's decimal support at its fullest).