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Page 84
READ POSITION
Command Descriptor Block
Field Descriptions
Read Position Data
The Read Position command reports the block address of the current data block.
The current data block is the first data block that would be read from the current tape
partition if a Read command were issued.
Bits
Byte
7
6
0
1
Ignored LUN
2
3
4
5
6
7
8
9
Field
Bytes
Bits
Operation
0
Code
Ignored
1
5-7
Logical
Unit
TCLP
1
2
Long
1
1
Reserved
2-8
Control
9
The Read Position command returns a block of Read Position Data. The following
table shows the fields in the Read Position Data when Long is 0.
5
4
3
Operation Code (34h)
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Control
Description
The Operation Code for Read Position is 34h.
The LUN field is residual from the SCSI-1 days and is ignored.
1 = The drive returns data specifying the partition, file and set
number with the current logical position.
0 = The drive returns data specifying the first and last block
location.
The Long bit and the TCLP bit must be equal, otherwise, the com-
mand shall be terminated with Check Condition status. The sense
key shall be set to Illegal Request, and the additional sense code
and an additional sense code qualifier set to Invalid Field in CDB.
1 = The drive shall return 32 bytes of data.
0 = The drive shall return 20 bytes of data.
The Long bit and the TCLP bit must be equal, otherwise, the com-
mand shall be terminated with Check Condition status. The sense
key shall be set to Illegal Request, and the additional sense code
and an additional sense code qualifier set to Invalid Field in CDB.
All reserved bits must be 0.
See Control Byte Format on page 18.
LTO SCSI Interface Manual
2
1
0
TCLP
Long
Reserved
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