CXD3018Q/R
§4-2. Frame Sync Protection
• In normal-speed playback, a frame sync is recorded approximately every 136µs (7.35kHz). This signal is
used as a reference to recognize the data within a frame. Conversely, if the frame sync cannot be
recognized, the data is processed as error data because the data cannot be recognized. As a result,
recognizing the frame sync properly is extremely important for improving playability.
• In the CXD3018Q/R, window protection and forward protection/backward protection have been adopted for
frame sync protection. These functions achieve very powerful frame sync protection. There are two window
widths: one for cases where a rotational disturbance affects the player and the other for cases where there is
no rotational disturbance (WSEL = 0/1). In addition, the forward protection counter is fixed to 13, and the
backward protection counter to 3. Concretely, when the frame sync is being played back normally and then
cannot be detected due to scratches etc., a maximum of 13 frames are inserted. If the frame sync cannot be
detected for 13 frames or more, the window opens to resynchronize the frame sync.
In addition, immediately after the window opens and the resynchronization is executed, if a proper frame
sync cannot be detected within 3 frames, the window opens immediately.
§4-3. Error Correction
• In the CD format, one 8-bit data contains two error correction codes, C1 and C2. For C1 correction, the code
is created with 28-byte information and 4-byte C1 parity.
For C2 correction, the code is created with 24-byte information and 4-byte parity.
Both C1 and C2 are Reed-Solomon codes with a minimum distance of 5.
• The CXD3018Q/R's SEC strategy uses powerful frame sync protection and C1 and C2 error correction to
achieve high playability.
• The correction status can be monitored externally.
See Table 4-2.
• When the C2 pointer is high, the data in question was uncorrectable. Either the previous value was held or
an average value interpolation was made for the data.
MNT3
MNT1
MNT0
Description
No C1 errors
0
0
0
1
1
1
0
0
1
0
0
1
0
1
1
0
1
0
One C1 error corrected
C1 correction impossible
No C2 errors
One C2 error corrected
C2 correction impossible
Table 4-2
– 66 –
ETC [ ETC ]
