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Section 23 CD-ROM Decoder
R01UH0134EJ0400 Rev. 4.00 Page 1255 of 2108
Sep 24, 2014
SH7262 Group, SH7264 Group
(3) ISY Interrupt
This interrupt can be generated in the following cases.
When a sync code was detected at a position where the value in the word counter (counter for
checking sync code intervals) was not correct and the sync code was ignored
When a sync code has not been detected although the word counter has reached the final value
and a sync code has been interpolated (for sync maintenance)
When a sync code was detected at a position where the value in the word counter (counter for
checking sync code intervals) was not correct and the sync code was used in resynchronization
When a sync code has not been detected although the word counter has reached the final value,
so the period taken up by the sector has been prolonged
When the sector has been processed as a short sector with the aid of interpolated sync codes
When the sector has been processed as a long sector with the aid of interpolated sync codes
(4) IERR Interrupt
This interrupt is generated in the following cases.
When ECC correction was incapable of correcting an error
When ECC correction was OK but the subsequent EDC check indicated an error
(5) IBUF Interrupt
This interrupt is generated when the following transitions occur.
Data transfer to the buffer Data transfer complete (searching for data for the next transfer)
Data for transfer to the buffer are being searched for Data transfer started
(6) IREADY Interrupt
This interrupt is generated when decoding of data for one sector is completed. This interrupt
should be used to start the CPU buffering stream data for output to SDRAM.
(7) DMA Transfer Request
The source of direct memory access controller activation is the same as that of IREADY. An
interrupt request is generated when output stream data for one sector becomes ready, and after the
2768 bytes of data shown in figure 23.15 have been transferred, the request signal is negated once.
This is because a certain amount of time is required before the output data for the next sector is
ready, so the transfer request from the direct memory access controller should be turned off
between transfers.