     $FDA3/64931:   Write SYNC 10240 times, erase track

    Jump from $FB0C:

    FDA3: AD 0C 1C  LDA $1C0C
    FDA6: 29 1F     AND #$1F        ; switch PCR to writing
    FDA8: 09 C0     ORA #$C0
    FDAA: 8D 0C 1C  STA $1C0C
    FDAD: A9 FF     LDA #$FF
    FDAF: 8D 03 1C  STA $1C03       ; port A (read/write head) to output
    FDB2: 8D 01 1C  STA $1C01       ; write $FF to disk
    FDB5: A2 28     LDX #$28        ; 40
    FDB7: A0 00     LDY #$00

    Jump from $FDB9, $FDBD, $FDC0:

    FDB9: 50 FE     BVC $FDB9       ; byte ready?
    FDBB: B8        CLV
    FDBC: 88        DEY
    FDBD: D0 FA     BNE $FDB9
    FDBF: CA        DEX
    FDC0: D0 F7     BNE $FDB9
    FDC2: 60        RTS

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