User's Guide

Chapter 3 Emulated DLT7000 SCSI Commands
Request Sense (03h)
248 Quantum DX-Series Software Interface Guide
drive. The tape drive returns information based on the non-diagnostic
data in its buffer as well as the data on tape medium. Additionally, bytes
25 through 28 contain the amount of tape to be written in 4 KB blocks.
REQUEST SENSE does not cause the drive to flush its buffered data to
tape. Therefore, if the host requires the exact physical positioning of the
tape medium, it should precede the REQUEST SENSE command with a
WRITE FILEMARKS command with length 0 (Immed=0) specified. This
forces the tape drive to flush any currently-buffered data to tape. A
subsequent REQUEST SENSE command returns the actual physical (and
logical) position of the tape drive to the initiator.
The following illustration portrays the format of REQUEST SENSE
DATA.
Table 201 REQUEST
SENSE - Data Format
Bit/Byte 7 6 5 4 3 2 1 0
0
Valid Error Code
1
Segment Number (0)
2
Filemar
k
EOM ILI Reserve
d
Sense Key
3-6
(MSB)
Information Bytes
(LSB)
7
Additional Sense Length
8-11
(MSB)
Command-Specific Information Bytes
(LSB)
12
Additional Sense Code (ASC)
13
Additional Sense Code Qualifier (ASCQ)
14
Sub-Assembly Code (0)
15
SKSV C/D Reserved BPV Bit Counter