Quantum ATL PowerStor L200 Series, User Manual

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Chapter 4 SCSI Interface
SCSI Message System
ATL PowerStor L200 Series Library User’s Guide 61
Save Data Pointer
(02h)
4
This message, sent from a target to the initiator, saves a copy of the
present active Data pointer for the logical unit currently attached.
As a target, the library 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
STATUS
phase. When received as a target,
it switches to message in phase and returns
MESSAGE REJECT
.
Synchronous Data
Transfer Request
(SDTR)
4
This extended message allows the target and initiator to agree on the
values of the parameters relevant to synchronous transfers. The library
will not initiate the Synchronous Data Transfer Request message, but
relies on the Initiator to do so. The SDTR message has the following
format:
Table 13 SDTR Extended
Message Format
Note: The library supports initiating synchronous transfer negotiations with
the host, but this feature is disabled by default. To enable it, set the
Mode Select VU ERROM parameter EnaInitSyncNeg.
Wide Data Transfer
Request (03h)
4
The following table shows the message formats.
Table 14 Wide Data
Transfer request (03h)
Byte 0 Extended Message Identifier (01h)
Byte 1 Length = (03h)
Byte 2 Message Code = (01h)
Byte 3 Transfer Period: min = 50= (32h)
Byte 4 Transfer Req/Ack Offset: max = 15
Bit
Byte
7 6 5 4 3 2 1 0
0 Extended Message (01h)
1 Extended Message Length (02h)
2 WIDE DATE TRANSFER REQUEST (03h)
3 Transfer Width Exponent