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Chapter 4: SCSI Commands
4-90
July 2004
81-81276-01 Rev A01
4.14.1 Combined Header and Data Mode
In this mode, the tape drive returns a 4-byte header followed by the data bytes. The tape drive
terminates the DATA IN phase when it has transferred Allocation Length bytes of header and data or
when it has transferred all available data to the initiator, whichever is less. Data bytes from the target
data buffer follow the 4-byte READ BUFFER header. The header has the following format:
Figure 4-61.
READ BUFFER Header for Combined Header and Data Mode — Data Format
Table 4-54.
READ BUFFER (3Ch) Command Descriptor Block — Field Descriptions
Field Name
Description
LUN
Logical Unit Number. The target ignores this field. Only an IDENTIFY message
can change the LUN.
Mode
The tape drive supports the following values within the field. If any unsupported
value is set, the tape drive terminates the command with a CHECK CONDITION
status and an ILLEGAL REQUEST Sense Key set.
Mode
Description
000b
Combined Header and Data
010b
Data
011b
Descriptor
Buffer ID
The tape drive supports only a single Buffer ID field of 0. If this field is nonzero,
the tape drive returns a CHECK CONDITION status with an ILLEGAL
REQUEST Sense Key set.
Offset
The tape drive does not support offsetting of data. If this field is nonzero, the tape
drive returns a CHECK CONDITION status with an ILLEGAL REQUEST Sense
Key set.
Allocation Length
This field specifies the maximum number of bytes that the initiator has allocated
for returned data.
Bit
Byte
7
6
5
4
3
2
1
0
0
Reserved
1 - 3
(MSB)
Available Length
(LSB)
Summary of Contents for DLT1/VS80 SCSI
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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