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P2 Assembly Instruction Size — Parallax Forums

P2 Assembly Instruction Size

expElecexpElec Posts: 27
in PASM2/Spin2 (P2)

I'm probably not seeing something obvious, but I've been getting familiar with the Assembly Manual and am looking at the COGINIT instruction.

The manual says the instruction is 7 bits, D is 6 bits, and it uses the lower 20 LSBs of S. If my math is correct that makes 33 bits. How does that fit into a 32 bit memory location?

Comments

  • expElecexpElec Posts: 27

    The format of Dest is %E_N_xVVV.

    Maybe that do-not-care bit gets ignored when assembled?

  • Wuerfel_21Wuerfel_21 Posts: 5,106

    You're mixing up the size of the instruction vs the size of the data it uses. D and S are always 9 bits and are either a register number or a 9 bit immediate. The immediate encoding can be extended to 32 bits using an AUGS/AUGD prefix.

  • expElecexpElec Posts: 27

    Ah, got it. Thanks.

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