6.5 Write Cache
(3) Status report in the event of an error
The status report concerning an error occurring during writing onto media is created when the next command is issued. Where the command reporting the error status is not executed, only the error status is reported. Only the status of an error that occurs during write processing is reported.
<Exceptions>
The error status is not reported in the following case:
•The COMRESET or software reset is received after an error has occurred during writing to media.
→The COMRESET or software reset processing is performed as usual. The error status that has occurred during writing to media is not reported.
(4)Enabling and disabling
Enabling and disabling of the Write Cache function can be set only with the SET FEATURES command. The setting does not changed even when the error status is reported.
The initial setting is stored in the system area of media. System area information is loaded whenever the power is turned on.
(5) COMRESET and software reset response
When a COMRESET or software reset is received while cached data is stored on the data buffer, data of the data buffer is written on the media, and reset processing is then performed. This is true for both a hard reset and soft reset.
(6) Cashing function when power supply is turned on
The cashing function is invalid until Calibration is done after the power supply is turned on.(about 10 sec) It is effective in Default after that as long as the cashing function is not invalidly set by the SET FEATURES command.
IMPORTANT
If Write Cache is enabled, there is a possibility that data transferred from the host with the Write Cache enable command is not completely written on disk media before the normal end interrupt is issued.
If an unrecoverable error occurs while multiple commands that are targets of write caching are received, the host has difficulty determining which command caused the error. (An error report is not issued to the host if automatic alternating processing for the error is performed normally.) Therefore, the host cannot execute a retry for the unrecoverable error while Write Cache is enabled. Be very careful on this point when using this function.
If a write error occurs, an abort response is sent to all subsequent commands.
