SCSI Commands
5-166
Quantum DLT 8000 Tape System
READ BUFFER Command (3Ch) (continued)
Table 5–74 READ BUFFER Command Descriptor Block — Field Descriptions
Field Name
Description
Mode
The tape drive supports the following values within this field. If any
non-supported value is set, the drive terminates the command with a
CHECK CONDITION status, ILLEGAL REQUEST sense key set.
Mode
Description
000b
Combined Header and Data (see 5.16.1)
010b
Data (see 5.16.2)
011b
Descriptor (see 5.16.3)
Buffer ID
Must be 0, 1, or 2.
Buffer 0: This 1100 KB buffer is intended to be used in conjunction
with the WRITE BUFFER command to provide a diagnostic
capability for testing the SCSI bus and/or hardware integrity.
Buffer 1: Choosing Buffer 1 results in the tape system transferring the
contents of controlled scratchpad RAM and EEPROM over
the SCSI bus. For DLT 8000 tape systems, a total of 264K is
transferred (256K for RAM, 8K for EEPROM).
Buffer 2: Choosing Buffer 2 results in the tape system transferring the
contents of data cache RAM over the SCSI bus. For DLT
8000 tape systems, a total of 8 MB is transferred.
Buffer Offset
The Buffer Offset field allows the host to specify where the start of
the data is within the buffer.
Allocation Length
This field specifies the maximum number of bytes that the initiator
has allocated for returning data. The host uses this field to limit the
size of data transfers to its own internal buffer size.
The host should first send a READ BUFFER command, in Descriptor mode, to
determine the size of the buffer being returned. In response to the READ BUFFER
command, the tape system returns four bytes of data, three of which contain the size of
the buffer. The host can then use this data to establish the Buffer Offset/Allocation
Length fields of the CDB. Once the size of the buffer is known, Mode 2 (Data Only, see
Section 5.16.2) can be used to transfer the data across the SCSI Bus.
Summary of Contents for DLTtape DLT 8000
Page 1: ...DLTTM 8000 Tape System Product Manual Nov 10 2003 81 60118 06...
Page 5: ...USER MANUAL STATEMENTS FOR CLASS B EQUIPMENT continued...
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Page 26: ...Table of Contents xxiv Quantum DLT 8000 Tape System...
Page 36: ...About This Manual Quantum DLT 8000 Tape System xxxii...
Page 54: ...General Description and Specifications 1 18 Quantum DLT 8000 Tape System...
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Page 376: ...Appendix A Definition of Vendor Unique Sense Data Information A 4 Quantum DLT 8000 Tape System...
Page 386: ...Appendix C Updating the Firmware C 6 Quantum DLT 8000 Tape System...
Page 396: ...Appendix E Visual Inspection Procedure for DLTtape Cartridges E 8 Quantum DLT 8000 Tape System...
Page 406: ...Appendix G DLT 7000 Emulation Feature G 8 Quantum DLT 8000 Tape System...
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