At the time that the drive has stopped the command execution after the error recovery has failed, the write cache function is disabled automatically. The releasing the disable state can be done by the SET FEATURES command. When the power of the drive is turned on after the power is turned off once, the status of the write cache function returns to the default state. The default state is “write cache enable”, and can be disable by the SET FEATURES command.
The write cache function is operated with the following command.
∙WRITE SECTOR(S)
∙WRITE MULTIPLE
∙WRITE DMA
IMPORTANT
When the write cache function is enabled, the transferred data from the host by the WRITE SECTOR(S) is not completely written on the disk medium at the time that the interrupt of command complete is generated. When the unrecoverable error occurs during the write operation, the command execution is stopped. Then, when the drive receives the next command, it generates an interrupt of abnormal end. However an interrupt of abnormal end is not generated when a write automatic assignment succeeds. However, since the host may issue several write commands before the drive generates an interrupt of abnormal end, the host cannot recognize that the occurred error is for which command generally. Therefore, it is very hard to retry the unrecoverable write error for the host in the write cache operation generally. So, take care to use the write cache function.
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