Chapter 3: SCSI Messages
3-8
July 2004
81-81276-01 Rev A01
3.2.15 SAVE DATA POINTER (02h)
A target sends this message to the initiator and saves a copy of the present active data pointer for the
logical unit currently attached.
As a target, the tape drive sends this message before a disconnect during a data transfer. It does not
send a SAVE DATA POINTER message if it intends to move directly to the STATUS phase.
When it receives the SAVE DATA POINTER message, the tape drive switches to the MESSAGE IN
phase and returns MESSAGE REJECT.
3.2.16 SYNCHRONOUS DATA TRANSFER REQUEST (SDTR)
This extended message allows the target and initiator to agree on the values of the parameters relevant
to synchronous transfers. The tape drive does not initiate the SYNCHRONOUS DATA TRANSFER
REQUEST (SDTR) message, but relies on the Initiator to do so.
Figure 3-3
shows the format for
extended messages.
Figure 3-3.
SDTR Extended Message Format
N
OTE
:
The tape drive supports initiating synchronous transfer negotiations with
the host, but this feature is disabled by default. To enable it, set the
MODE SELECT Vendor Unique EEPROM parameter EnaInitSyncNeg.
3.2.17 WIDE DATA TRANSFER REQUEST (WDTR)
The WDTR message exchange establishes an agreement between two SCSI tape drives on the width of
the data path to be used for DATA phase transfer between the two tape drives. All other information
transfer phases use an eight-bit data path.
Bit
Byte
7
6
5
4
3
2
1
0
0
Extended Message Identifier (01h)
1
Extended Message Length (03h)
2
SYNCHRONOUS DATA TRANSFER REQUEST (01h)
3
Transfer Period: min = 100ns (19h)
4
Transfer REQ/ACK Offset: max = 15 (0Fh)
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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