User's Guide

Commands: Read Position (34h) Page 119
READ POSITION (34h)
The READ POSITION command reports the block address of the current logical
block. The current logical block is the first logical block that would be read from the
current tape partition if a READ command were issued.
READ POSITION Command Descriptor Block
The following table shows the layout of the CDB.
Byte
Bits
7 6 5 4 3 2 1 0
0 0 0 1 1 0 1 0 0
1 0 0 0 0 0 TCLP Long BT
2 0 0 0 0 0 0 0 0
3 0 0 0 0 0 0 0 0
4 0 0 0 0 0 0 0 0
5 0 0 0 0 0 0 0 0
6 0 0 0 0 0 0 0 0
7 0 0 0 0 0 0 0 0
8 0 0 0 0 0 0 0 0
9 vendor unique* 0 0 0 0 Flag Link
* This vendor-unique field is reserved and must be set to zero.
READ POSITION Command Descriptor Block Field Descriptions
The following table lists field descriptions for the CDB.
Field
Name Bytes Bits Description
TCLP 1 2 1 = The drive returns data specifying the partition, file and set number
with 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 command
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.
Long 1 1 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 command 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.
BT bit 1 0 If the BT bit is 0, the Block Location is the total number of logical blocks,
filemarks and setmarks from the beginning of the partition. If the BT bit
is 1 the Block Location is the total number of logical blocks from the
beginning of the partition; filemarks and setmarks are ignored and not
counted in this mode.