RegLoop$:
    ; Copy register number and write to YM
    ld      a, (de)
    add     c
    ld      (YM2612_Reg1), a
    inc     de

    ; ...and write the appropriate value.
    ld      a, (hl)
    ld      (YM2612_Dat1), a
    inc     hl

    ; Repeat until all registers have been written.
    djnz    RegLoop$
    jp      FM_UpdatePan