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DLT1/VS80 SCSI Interface Guide
81-81276-01 Rev A01
July 2004
4-47
Table 4-28.
MODE SELECT (6) Parameter List — Field Descriptions
Field Name
Description
Media Type
The MODE SELECT command ignores this field.
Buffered Mode
The tape drive implements Immediate Reporting on WRITE commands through
Buffered mode.
If the field is 0, the tape drive does not report a GOOD status on WRITE
commands until the data blocks are actually written to medium. If the Buffered
Mode field is 1, the default configuration, the tape drive reports GOOD status on
WRITE commands as soon as the data block has been transferred to the buffer.
When Buffered Mode is not used, the tape drive suffers a degradation in
performance and possibly capacity as well, depending on medium format, block
size, and compression. When writing and the block size is a multiple of 8 KB,
there should be no capacity loss.
Turning off Buffered Mode essentially disables the block packing feature.
If this field is greater than 1, the command is rejected with a CHECK
CONDITION, with a Sense Key of ILLEGAL REQUEST.
Speed
The tape drive supports only one speed, the default speed.
Block Descriptor
Length
Specifies the length, in bytes, of all the block descriptors. Since the tape drive only
allows one block descriptor, this value must be 8 or 0. Any other value causes a
CHECK CONDITION status with an ILLEGAL REQUEST Sense Key to be
returned.
Density Code
This field should match the current density of the media. If this value is 0, the tape
drive uses default density.
Density Code
00h
40h
7Fh
86h
87h
Description
Use default density
DLT1 format, DLTtapeIV – 40 GB
No changes from previous density (No operation)
DLT1 format, DLTtapeIV – 40 GB
without compression
DLT1 format, DLTtapeIV – 80 GB
with compression
Number of Blocks
This MODE SENSE field is sent as 0, indicating that all of the remaining logical
blocks on the medium have the medium characteristics specified by the block
descriptor.
Block Length
This specifies the length, in bytes, of each logical block transferred over the SCSI
bus. A block length of 0 indicates that the length is variable (specified in the I/O
command). Any other value indicates the number of bytes per block to use for
READ, WRITE, and VERIFY type commands that specify a “Fixed” bit of 1 (i.e.,
fixed block mode) which also causes the transfer length in the CDB to be defined
as a block count.
Summary of Contents for DLTtape DLT1
Page 1: ...DLT1 VS80 SCSI Interface Guide...
Page 6: ...DLT1 VS80 SCSI Interface Guide vi July 2004 81 81276 01 Rev A01 Notes...
Page 12: ...Table of Contents xii July 2004 81 81276 01 Rev A01 Notes...
Page 16: ...List of Figures xiv July 2004 81 81276 01 Rev A01 Notes...
Page 20: ...List of Tables xviii July 2004 81 81276 01 Rev A01 Notes...
Page 24: ...Chapter 1 Introduction 1 4 July 2004 81 81276 01 Rev A01 Notes...
Page 32: ...Chapter 2 General SCSI Bus Operation 2 8 July 2004 81 81276 01 Rev A01 Notes...
Page 42: ...Chapter 3 SCSI Messages 3 10 July 2004 81 81276 01 Rev A01 Notes...
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