Samsung DVD-808K, Service Manual

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7-12
Samsung Electronics
7-4 DVD Data Processor
7-4-1 Outline
DIC1(TC90A19F) performs PLL(Phase Locked Loop), Sync detection, demodulation and error correction after con-
verting RF signal inputted at DVD regeneration into digital data.
TC90A19F uses external memory(DIC2, 4M DRAM, KM48C512BLJ) as buffer as well as for error correction and
carries out Variable Bit Rate transfer function. VBR function uses the external buffer as buffer to absorb the differ-
ence of transfer rate occurring because the transfer rate of disc playback is faster than data transfer rate demand-
ed by MPEG decoder(Video/Audio Signal Process Chip).
In case of general disc refresh, the memory is almost filled up periodically. It is because Write rate to memory after
disc playback and signal process is faster than Read rate of MPEG decoder. When the memory is filled, this sta-
tus is reported by interrupt to main micom, which controls the servo to kick back the pick-up to the previous track
after memorizing the last data read from disc until now. It takes some times to jump to the previous track and return
to the original position(jump location) again. The memory will have an empty space because MPEG decoder reads
out data of memory.
When the memory has an empty space, where data can be processed and written and the pick-up correctly gets to
the original location(before kick back location) again, it reads data again and avoids the interrupt of data read pre-
viously.
The basic operation repeats to perform (disc data read --> memory full --> move pick-up to previous track --> disc
data read --> memory full --> move pick-up to previous track) as described above.