Seagate ST3285N, Product Manual

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3.4.6 Read command (08
H
)
When the drive receives the Read command, it transfers data to the
initiator.
The Error Recovery page (01
H
) determines how the drive handles errors
during a Read command. The Error Recover page is discussed in
Appendix C.1.
If there is a reservation access conflict, this command terminates with a
reservation conflict status and no data is read. For more information
about the reservation conflict status, see Section 3.2.
In systems that support disconnection, the drive disconnects when a valid
Read command is received, unless the data is available in the cache
buffer and the drive does not need to access the disc. The buffer full ratio
byte of the Disconnect/Reconnect page determines when the drive
reconnects. (The Disconnect/Reconnect page is discussed in Sec-
tion C.2.) After the drive starts transferring data to the initiator, the drive
does not disconnect unless an internal error recovery procedure is
required or the data transfer to an initiator is interrupted for more than
1 millisecond.
Because the drive uses read look-ahead and caching functions, it may
read more data into the buffer than specified by the transfer length in the
CDB.
Bit
Byte
7 6 5 4 3 2 1 0
0 0 0 0 0 1 0 0 0
1 LUN Logical block address (MSB)
2 Logical block address
3 Logical block address (LSB)
4 Transfer length
5 Control byte (00
H
)
Bytes 1–3 The logical block address specifies the logical block where
the read begins.
Byte 4 The transfer length specifies the number of contiguous
logical blocks of data to be transferred. A transfer length
of 0 indicates that 256 logical blocks are to be transferred.
Any other value indicates the number of logical blocks to be
transferred.
44 ST3655 Family SCSI Drives Product Manual, Rev. A