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CXD2598Q
§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 CXD2598Q, 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 set to 13
, and the
backward protection counter to 3
. Concretely, when the disc is being played back normally and then the
frame sync 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.
Default values. These values can be set as desired by the SFP3 to SFP0 and SRP3 to SRP0 commands of $C.
§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 CXD2598Q uses refined super strategy to achieve double correction for C1 and quadruple correction for
C2.
In addition, to prevent C2 miscorrection, a C1 pointer is attached to data after C1 correction according to the
C1 error status during C1 error correction, the playback status of the EFM signal, and the operating status of
the player.
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 pre-value was held or an
average value interpolation was made for the data.
MNT3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
No C1 errors;
C1 pointer reset
One C1 error corrected;
C1 pointer reset
—
—
No C1 errors;
C1 pointer set
One C1 error corrected;
C1 pointer set
Two C1 errors corrected;
C1 pointer set
C1 correction impossible;
C1 pointer set
No C2 errors;
C2 pointer reset
One C2 error corrected;
C2 pointer reset
Two C2 errors corrected;
C2 pointer reset
Three C2 errors corrected;
C2 pointer reset
Four C2 errors corrected;
C2 pointer reset
—
C2 correction impossible;
C1 pointer copy
C2 correction impossible;
C2 pointer set
MNT2
MNT1
MNT0
Description
Table 4-2.