Hitachi ULTRASTAR 15K450 HUS154530VLF400 - Manual (Page 232)

Hitachi Ultrastar 15K450 (FC-AL) Hard Disk Drive Specification
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19.20.1 Combined Header And Data (Mode 00000b)
In this mode a 4-byte header followed by data bytes is returned to the Initiator during the DATA IN phase. The Buffer ID and
the buffer offset field are reserved.
The drive terminates the DATA IN phase when allocation length bytes of header plus data have been transferred or when the
header and all available data have been transferred to the Initiator, whichever is less.
The 4-byte READ BUFFER header (see figure below) is followed by data bytes from the data buffer of the drive.
Table 181: Read Buffer Header
The buffer capacity specifies the total number of data bytes that are available in the data buffer of the drive. This number is not
reduced to reflect the allocation length nor is it reduced to reflect the actual number of bytes written using the WRITE BUF-
FER command.
Following the READ BUFFER header the drive will transfer data from its data buffer.
Byte
Bit
7 6 5 4 3 2 1
0 RSVD = 0
1-3
(MSB) Buffer Capacity
(LSB)