User Manual

SCSI Commands Reference Manual, Rev. J 171
www.seagate.com Direct Access Block commands (SPC-5 and SBC-4)
ALLOCATION LENGTH field
The ALLOCATION LENGTH field (see 2.2.6) shall specify the number of bytes the initiator has allocated for returned data. An ALLOCATION
LENGTH of zero indicates that no data shall be transferred. Any other value indicates the maximum number of bytes that shall be transferred.
The drive terminates the DATA IN phase when ALLOCATION LENGTH bytes have been transferred or when all available data has been trans-
ferred to the initiator, whichever is less.
[1] ADDITIONAL LENGTH. This two byte value indicates the number of additional bytes included in the diagnostic data list.
For example, if no product unique byte (byte 7) is available, this value would be 0006h. A value of 0000h means that there
are no additional bytes.
[2] A FIELD REPLACEABLE UNIT (FRU) Code is a byte that identifies an assembly that may have failed. The codes will be listed
in probability order, with the most probable assembly listed first and the least probable listed last. A code of 00h indicates
there is no FRU information and a code of 01h indicates the entire unit should be replaced. Seagate drives return 00h in
these bytes.
[3] The ERROR CODE is a two byte value that provides information designating which part of a diagnostic operation has
failed. The LSB of the error code is vendor unique and defined in note
[4]. Usually, Seagate drives support only some sub-
set of the list given in note [4].
[4] Vendor Unique codes supported by Seagate devices are listed in table 138.
Table 137 Diagnostic Data Bytes
Code Byte Description
00h 0 ADDITIONAL LENGTH (MSB) [1]
28h 1 ADDITIONAL LENGTH (LSB) [1]
XXh 2 FRU CODE (most probable) [2]
XXh 3 FRU CODE [2]
XXh 4 FRU CODE [2]
XXh 5 FRU CODE (least probable) [2]
XXh 6 ERROR CODE (MSB) [3]
V.U. 7 ERROR CODE (LSB) [4]
V.U. 8 thru n Additional vendor unique fault information (if any) (not available)