Interrupt causes:

        i=0  -> reset,
        i=1  -> ill,
        i=2  -> imal OR dmal,
        i=3  -> ipf,
        i=4  -> dpf,
        i=5  -> trap,
        i=6  -> ovf,
// fpu
        i= 7 -> OVF,
        i= 8 -> UNF,
        i= 9 -> INX,
        i=10 -> DIVZ,
        i=11 -> INV,
        i=12 -> UNIMPL,

SPR:
    SR   =0;
    ESR  =1;
    ECA  =2;
    EPC  =3;
    EDPC =4;
    EData=5;
    RM   =6;
    IEEEf=7;
    FCC  =8;