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Section 23 CD-ROM Decoder
R01UH0134EJ0400 Rev. 4.00 Page 1247 of 2108
Sep 24, 2014
SH7262 Group, SH7264 Group
(4) Interpolated Sync Plus External Sync Mode
In interpolated sync plus external sync mode, synchronization is based on the detected sync code
patterns as long as they are present, and if a sync pattern is not detected at the 2352nd byte, the
sync code maintenance is applied. Synchronization in this mode is more quickly responsive to
changes in synchronization timing than synchronization in the automatic sync maintenance mode.
However, decoding still becomes incorrect when a sync pattern is input with abnormal timing.
Figures 23.13 and 23.14 show the operation in interpolated sync plus external sync mode in the
cases of abnormally short and long sectors, respectively.
Abnormal
sector
Input data
Sync code
detection
Output data
Maintain
Sector 1
Sector 1 Sector 3 Sector 4 Sector 5
Sector 4Sector 3 Sector 5 Sector 6
Abnormal sector
Figure 23.13 Operation in Interpolated Sync Plus External Sync Mode
(When an Abnormally Short Sector is Encountered)
Sector 1 Sector 4Sector 3
Abnormal
sector
Abnormal
sector
Input data
Sync code
detection
Output data
Maintain
Sector 1 Sector 4Sector 3 Sector 5
Abnormal sector
Figure 23.14 Operation in Interpolated Sync Plus External Sync Mode
(When an Abnormally Long Sector is Encountered)