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unused/undocumented instructions — Parallax Forums

unused/undocumented instructions

fkifki Posts: 10
edited 2011-08-03 11:13 in Propeller 1
Hi,

having a look at p 254 and p255 in PropellerManual v1.1 i see, that the instr-codes
0001xx (000100, 000101, 000110 and 000111) are missing.

Does anyone know, if they are "illigal" or if their behaviour is just "not usefull"?
Will they be used in the future?

Greetings
FKi

Comments

  • AleAle Posts: 2,363
    edited 2011-08-03 05:04
    Those are unimplemented instructions for the propeller 1. They should behave as NOPs. The next propeller (Prop 2) has a somewhat different opcode map and these are definitely used. While some opcodes remain in place, there are plenty of new ones not only in these slots but also where HUPOP lays.
  • kuronekokuroneko Posts: 3,623
    edited 2011-08-03 06:14
    Unfortunately they are not nops (IIRC dst is always cleared). Then again, given that they are marked as not implemented you shouldn't use them anyway.
  • StefanL38StefanL38 Posts: 2,292
    edited 2011-08-03 11:13
    But I guess it would be interesting to analyse what these OP-codes do.
    Of course the prop is far away from a 6502 or x86 but I remember that there were some curoius things. I Don't remember them really but it was something crazy like
    "increment x-register and jump to offset Y" all done in a single illegal instruction.

    best regards

    Stefan
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