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Section 23 CD-ROM Decoder
Page 1244 of 2108 R01UH0134EJ0400 Rev. 4.00
Sep 24, 2014
SH7262 Group, SH7264 Group
(1) Automatic Sync Maintenance Mode
In automatic sync maintenance mode, the sync code is ignored if detected within the one-sector
(2352-byte) period. Furthermore, if a sync code is not detected at the point where a next sector
should start, sync code maintenance is applied. If synchronization timing has changed, re-
synchronization is performed at the point where a sync code is detected within 2352 bytes after the
change.
Therefore, this mode is effective in rejecting abnormal sync patterns and following changes in
synchronization timing. Note, however, that this mode cannot achieve synchronization with the
first sector after a change to the synchronization timing.
Figure 23.8 shows operation in the case of normal sync-code detection, figure 23.9 shows a case
where a sync code is detected before a current one-sector period has elapsed, and figure 23.10
shows the case where the actual sync code is only detected some time after a full one-sector period
has elapsed.
Input data
Sync code detection
Output data
Sector 1
Sector 1 Sector 2 Sector 3 Sector 4 Sector 6
Sector 2 Sector 3 Sector 4 Sector 5 Sector 6
Figure 23.8 Operation in Automatic Sync Maintenance Mode (Normal Timing)
Input data
Sync code
detection
Output data
Sector 1
Abnormal sector
Abnormal
sector
Ignore Maintain Ignore Maintain
Re-synchronization
Abnormal
sector
Abnormal
sector
Sector 1 Sector 5
Sector 3 Sector 4 Sector 5 Sector 6
Figure 23.9 Operation in Automatic Sync Maintenance Mode
(When an Abnormally Short Sector is Encountered)