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Propeller 2 Invalid Instruction behavior — Parallax Forums

Propeller 2 Invalid Instruction behavior

moonymoony Posts: 27
in Propeller 2
Does anyone know what P2 cogs do when they encounter an invalid operation? E.g. the two empty slots documented in the spreadsheet, and the many undocumented empty slots. Do they NOP, halt, or engage in undefined behavior?

Comments

  • RaymanRayman Posts: 13,859
    I’d guess it’s undefined. Better to not do that :)
  • Cluso99Cluso99 Posts: 18,069
    AFAIK it's undefined. It really depends on how the decode treats the instruction bitcodes that are undefined. They may execute parts of instructions. That's what you get when you don't fully decode something, but the benefit is that you use less silicon that may end up allowing the chip to run faster because critical paths have been reduced.
  • pik33pik33 Posts: 2,350
    edited 2020-12-25 08:44
    Rayman wrote: »
    I’d guess it’s undefined. Better to not do that :)
    As we, 6502 veterans, know, if there is an undefined opcode, it has to be tried :)
  • moonymoony Posts: 27
    pik33 wrote: »
    Rayman wrote: »
    I’d guess it’s undefined. Better to not do that :)
    A we, 6502 veterans, know, if there is an undefined opcode, it has to be tried :)

    Exactly why I asked :)
  • cgraceycgracey Posts: 14,133
    It will be like a NOP.
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