Hitachi ULTRASTAR 15K450 HUS154530VLF400 - Manual (Page 315)

Hitachi Ultrastar 15K450 (FC-AL) Hard Disk Drive Specification
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19.59.6 Write Data to Echo Buffer (Mode 01010b)
In this mode the Target transfers data into the echo buffer. The echo buffer is assigned in the same manner by the Target as it
would for a WRITE operation. Data will be sent aligned on 4-byte boundaries.
Upon successful completion of a WRITE BUFFER command the data will be preserved in the echo buffer unless there is an
intervening command to any logical unit, in which case it may be changed.