; =============== S U B R O U T I N E =======================================
_rand:
        LDA _rand_seed
        BNE loc_61A76F
        LDA _nmi_is_over_flag
        STA _rand_seed
loc_61A76F:
        LDA _rand_seed
        AND #2
        STA _rand_seed+4
        LDA _rand_seed+1
        AND #2
        EOR _rand_seed+4
        CLC
        BEQ loc_61A783
        SEC
loc_61A783:
        ROR _rand_seed
        ROR _rand_seed+1
        ROR _rand_seed+2
        ROR _rand_seed+3
        ROR _rand_seed+5
        ROR _rand_seed+6
        ROR _rand_seed+7
        ROR _rand_seed+8
        ROR _rand_seed+9
        ROR _rand_seed+$A
        ROR _rand_seed+$B
        ROR _rand_seed+$C
        ROR _rand_seed+$D
        ROR _rand_seed+$E
        ROR _rand_seed+$F
        ROR _rand_seed+$10
        ROR _rand_seed+$11
        ROR _rand_seed+$12
        ROR _rand_seed+$13
        ROR _rand_seed+$14
        ROR _rand_seed+$15
        ROR _rand_seed+$16
        ROR _rand_seed+$17
        ROR _rand_seed+$18
        ROR _rand_seed+$19
        ROR _rand_seed+$1A
        ROR _rand_seed+$1B
        RTS