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Motorola 68020 SUB instruction

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  • 12-12-2019 1:57pm
    #1
    funkey_monkey
    Registered Users Posts: 8,224 ✭✭✭ 


    SUB.W R0, 0, R3

    The Carry flag is set if the operation borrowed. Essentially, what is happening here is that R3 is negated (0 - R3) and if this requires a borrow, then the Carry Flag is set for R0.

    How does this work? I can't figure out how it is set. The code using this Carry flag to determine if the least significant bit in R3 is 0 or 1.

    Thanks.


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