Quantum Quantum Atlas 10K II 9.2/18.4/36.7/73.4 GB, Product Manual

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SCSI Description
Quantum Atlas 10K II Ultra160/m SCSI Hard Disk Drives 5–137
5.21 READ (10) Command (28h)
The READ (10) command requests that data be transferred from the drive to the
initiator. The amount of data transferred is specified by the transfer length field. The
starting point is specified by the logical sector address.
Bit
Byte
7 6 5 4 3 2 1 0
0 Operation Code (28h)
1 Reserved DPO FUA Reserved RelAdr
2 - 5 Logical Block Address
6 Reserved
7 - 8 Transfer Length
9 Control
Figure 5–57 READ (10) Command — Data Format
Table 5–64 READ (10) Command — Field Descriptions
Field Description
DPO Disable Page Out. When the value is 0, the drive caches the data read,
using its normal Logical Read Unit policies.
When the value is 1, the drive assigns to logical blocks accessed by the
READ (10) command the lowest priority for being fetched into or
retained by the cache.
FUA Force Unit Access. When the value is 0, the drive is allowed to satisfy the
read with cache-resident data.
A value of 1 indicates that the drive accesses the media in performing
the command before returning GOOD status.
RelAdr Relative Addressing. The drive does not support relative addressing. Must
be 0.
Logical Block Address Specifies the logical sector address where the read operation will begin.
Transfer Length Specifies the number of contiguous logical blocks of data to transfer. A
transfer length of 0 indicates that no logical blocks are to be transferred.
Any other value indicates the number of logical blocks to be transferred.
The drive returns a CHECK CONDITION status with the correct sense data
if the specified transfer extends beyond the logical sector space.