Scalar DLC Reference Guide
271
SCSI Message System
The SCSI message system (Message In/Message Out) allows communication between an initiator and a
target for the purpose of physical path management.
Transfer
The library supports asynchronous data transfer phases with differential and single
ended communications. Odd parity is generated during all information transfer phases
from the library. Parity is checked during all information transfer phases to the library.
Parity checking can be disabled.
Information Transfer phases include:
• The Message In/Message Out phases manage the physical path between the host
initiator and target destination. Message In is a message to the host initiator, Message
Out is a message to the target destination.
• Command Out phase is a command from the host initiator to the target destination.
• Data In/Data Out phase is either data sent from the target to the host initiator (Data
In) or data sent from the host initiator to the target destination (Data Out).
• Status In is a target status byte response to a host-initiated command.
Message
Code
Description
Direction
COMMAND
COMPLETE
00h
The COMMAND COMPLETE message is
sent from a target to an initiator to indicate that
the execution of a command is complete and
valid status has been sent to the initiator.
In
SAVE DATA
POINTERS
02h
The SAVE DATA POINTERS message is
issued before every disconnect message
following a Data In or Data Out phase. The
message is not sent when disconnecting after
a Command Descriptor Block (CDB) that did
not transfer data.
In
RESTORE
POINTERS
03h
The RESTORE POINTERS message is sent
from a target to direct the initiator to continue
sending data.
In
DISCONNECT
04h
The DISCONNECT message is sent by a
target to inform an initiator that the present
data transfer will be suspended. The target
will reselect the initiator at a later time to
continue the current operation.
In
INITIATOR
DETECTED ERROR
05h
The INITIATOR DETECTED ERROR
message is sent from an initiator to inform a
target that an error has occurred. This allows
the target to retry the operation.
Out
ABORT
06h
The ABORT message is sent from the initiator
to the target to clear the current or pending
operation. The target goes directly to the BUS
FREE phase after successful receipt of this
message.
Out
Phase
Description
Summary of Contents for Scalar 1000
Page 14: ...xiv Figures...
Page 86: ...70 Management GUI...
Page 188: ...172 Configuration Tab...
Page 198: ...182 Events Tab...
Page 254: ...238 Tools and Utilities...
Page 282: ...266 DAS Guide...
Page 292: ...276 SCSI Guide...
Page 300: ...284 ROBAR Guide...
Page 304: ...288 Index...