Command Link - Fujitsu MAX3073NC - SCSI,80, Dell DC961,Hard Drive Scsi Logical Interface Specifications

4) The TARG executes the COMMAND phase and receives the CDB from the INIT. The TARG
judges the length of the CDB by the group code in the first byte of the CDB and requests transfer of
the necessary number of bytes.
5) The TARG investigates the contents of the command and executes the requested operation. In the
case of commands for which data transfer on the SCSI bus is necessary, the DATA IN or the DATA
OUT phase is executed.
6) When execution of the command is completed, the TARG reports the execution results by the status
in the STATUS phase to the INIT.
7) The TARG reports the TASK COMPLETE message to the INIT in the MESSAGE IN phase and
enters the BUS FREE phase.
1.3.2

Command link

The command link function is a function which causes the TARG to execute continuous processing of
multiple commands. Following shows examples of command link processing.
1) The INIT sets the initial values for the command in the command pointer, data pointer and status
pointer.
2) Obtaining the SCSI bus usage, selection of the TARG and specification of the LUN by the
IDENTIFY message are the same as in the case of single command.
3) The TARG receives commands from the INIT in the COMMAND phase, but "1" is specified in the
Link bit of the control byte of the CDB.
4) The TARG analyzes the command and executes the requested processing.
5) If processing of the command is completed normally, the TARG reports the INTERMEDIATE status
in the STATUS phase to the INIT. At this time, the command link function becomes effective.
6) The TARG informs the INIT of the LINKED TASK COMPLETE. When the INIT has received the
LINKED TASK COMPLETE message, the command, data and status pointers are updated to the
initial values for the next linked command.
7) The TARG enters the COMMAND phase immediately after the MESSAGE IN phase and receives
the command to be executed next. After that, it performs either single command (Link bit = "0")
processing or command link (Link bit = "1") processing.
The command link continues until a command with "0" specified in the Link bit of its CDB is issued or
until a command terminates abnormally.
The command link function is made effective only in the case that commands with link specifications are
completed normally. If a command with a link specification is completed in an error state or in an
exception state, the command link function is invalidated. Table 1.1 shows the response of the IDD when
commands with a Link specification are terminated.
C141-C010
1.3 Outline of Command Processing
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