
Chapter 2 Messages
Supported SCSI Messages
Quantum ATL SuperLoader Software Interface Guide 21
Synchronous Data
Transfer Request
(01h)
2
This extended message allows the target and initiator to agree on
the values of the parameters relevant to synchronous transfers. The
SuperLoader will not initiate the SYNCHRONOUS DATA
TRANSFER REQUEST message; it relies on the initiator to do so.
The SYNCHRONOUS DATA TRANSFER REQUEST message has
the format shown in figure 4
.
Figure 4 Synchronous
Data Transfer Request
Message
A SYNCHRONOUS DATA TRANSFER REQUEST message
exchange is initiated by a SCSI device whenever a previously
arranged transfer width agreement may have become invalid. The
agreement becomes invalid after any condition that may leave the
data transfer agreement in an indeterminate state such as:
• After a hard reset condition
Note: The SuperLoader DLT supports initiating synchronous
transfer negotiations with the host, but this feature is
disabled by default. To enable it, set the MODE SELECT
VU EEROM parameter EnaInitSyncNeg.
Bit
Byte76543210
0
Extended Message Identifier (01h) (see figure 1)
1
Length (03h)
2
SYNCHRONOUS DATA TRANSFER REQUEST (01h)
3
Transfer Period
4
Transfer REQ/ACK Offset
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