FMsetParam:
;   d3 = port
;   d4 = part1or2
;   d5 = data
    movem.l d4/a1-a2, -(a7)
    lea ($A04000), a1
    lea ($A04001), a2
    and.l #$FFFFFF00, d4
    add.b d4, d4
    add.l d4, a1
    add.l d4, a2
    move.b d3, (a1)
    move.b d5, (a2)
    movem.l (a7)+, d4/a1-a2
    rts

FMNoteOn
    movem.l d3-d5/a0-a2, -(a7)
    move.l d3, d5
    lea ($A04000), a1
    lea ($A04001), a2
    btst #3, d3
    beq.s NoteON_NoSet
    subq.b #4, d3
    add.l #2, a1
    add.l #2, a2
NoteON_NoSet:
    WaitYM
    add.b #$A4, d3
    move.b d3, (a1)
    ror.w #8, d4
    move.b d4, (a2)
    WaitYM
    subq.b #4, d3
    move.b d3, (a1)
    rol.w #8, d4
    move.b d4, (a2)
    WaitYM
    move.b #$28, (a1)
    move.b d5, (a2)
    WaitYM
    or.b #%11110000, d5
    move.b d5, (a2)
    movem.l (a7)+, d3-d5/a0-a2
    rts

LoadFM:
    movem.l d3-d4/a0-a2, -(a7)
    ;a0 = instrument
    ;d3 = channel
    lea ($A04000), a1
    lea ($A04001), a2
    btst #3, d3
    beq.s LoadFM_NoSet
    add.l #2, a1
    add.l #2, a2
LoadFM_NoSet:
    add.b #$B0, d3
    WaitYM
    move.b d3, (a1)
    move.b (a0)+, d4
    or.b #$C0, d4
    move.b d4, (a2)
    sub.b #$80, d3
    moveq.l #$1B, d4
LoadFM_Loop
    WaitYM
    move.b d3, (a1)
    move.b (a0)+, (a2)
    addq.b #4, d3
    dbf d4, LoadFM_Loop
    movem.l (a7)+, d3-d4/a0-a2
    rts