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OD-A017-02
TOSHIBA DVD-RAM SD-W1111 ‘99/06/26 Version 1.0
Page 28 Product Specification
14. Notes on data guarantee
14.1 Disappearance of data in buffer in a write cache operation
In a write cache operation, before data are actually written to a disc, a status response to the WRITE
command or WRITE & VERIFY command is sent. If the power supply is switched off immediately
after the status response, there is a possibility that the data in the buffer will disappear before being
written to the disc. To avoid this problem, execute FLUSH CACHE command before switching off
the power supply.
Always execute FLUSH CACHE command before switching off the power supply, to avoid any risk
of disappearance of data in buffer.
14.2 Error report in a write cache operation
When an error which cannot be recovered before all the data is received and written in the buffer and
a status response to the command is sent in the write cache operation, the error is reported as 71H in
REQUEST SENSE DATA. This shows that the error occurred on the last WRITE command or
WRITE & VERIFY command.
14.3 Automatic sector replacement at a write operation
When data can not be written to the disc normally due an unrecoverable error, such as ID NOT
FOUND, the drive replaces the sector by sector replacement processing. The drive prevents data
from being lost by this operation as much as possible. Because automatic sector replacement
processing is executed after write retry ends in an error, a time of between 7 to 15 seconds is needed.
Therefore, it is recommended that the time-out to the command generating access to the disc is set at
20 seconds or more. In a write cache operation, when automatic sector replacement processing is
done after a status response to the command is send, execution of the following command can be
made to wait. However, when the following command is a WRITE command or WRITE & VERIFY
command, the first data transfer of one block is executed without waiting, to prevent a time-out of the
host.
14.4 Verification of a block address
When the command is received, a drive calculates block addresses where the data are written or read,
with the start address and length specified by the command, and verifies whether the block addresses
contain a block address which does not exist. If such a block address exists is founded, the drive does
not record nor read, and reports on the error to the command at once.
14.5 Error generation in Read Modify Write operation
If, in a WRITE command and WRITE &VERIFY command, a start address number is not other than
*****0H or a block length is other than *16 x (integer)* though the start address number is *****0H,
the drive reads all data in an ECC block which contain the specified address once, and replaces the
data in the ECC block by the data of the specified address. This chain of operations is called "Read
Modify Write Operation". In "Read Modify Write Operation", in WRITE command and
WRITE&VERIFY command, an error occurs when the data of the ECC block cannot be read for
some reasons.