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Chapter 4 SCSI Interface
SCSI Message System
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
Table 13 SDTR Extended
Message Format
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:
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
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)
Table 14 Wide Data
Transfer request (03h)
The following table shows the message formats.
4
Bit
7
6
5
4
3
2
1
0
Byte
0
Extended Message (01h)
1
Extended Message Length (02h)
2
WIDE DATE TRANSFER REQUEST (03h)
3
Transfer Width Exponent
ATL PowerStor L200 Series Library User’s Guide
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