S1R72105 Technical Manual
60
EPSON
Rev.1.0
7.6.3 Command Execution and Change of State
The IC goes through the following three states from the viewpoint of execution of SCSI-type commands:
Disconnected state (D)
Connected state in Initiator mode (I)
Connected state in Target mode (T)
Changes in these states caused by specific commands are as shown in the figure below:
D
WAIT_SCAM_SELECT_COMMAND
SELECT
***
WAIT_SELECT_COMMAND
WAIT_RESELECT RESELECT
BUSFREE
ASSERT_RST
I T
Change from I to D takes place implicitly except that by the Assert_RST command.
It means that there is no command that causes such change explicitly. If busfree is found when the next
connection-type command is issued, it is assumed to be the disconnected state and the command is executed.
If busfree is not found, the disconnected state is waited for and the connection-related command is put on hold.
The connection-type command can be executed in the disconnected state. It may be issued in such state.
If it is issued while the SCSI control command is being executed, however, a command error occurs.
A transfer-type command can be executed in the connected state. If it is issued in the disconnected state, a
command error occurs.
Both connection- and transfer-type commands can be executed when the IC is in the condition where no SCSI
control command is being executed.
If they are issued while SCSI control command is in execution, a command error occurs.
7.7 Others and Cautions in Operation
Operation responding to the selection without the SCSI-1 arbitration phase
The IC operates as mentioned below in response to the selection of only target ID of SCSI-1. Note that there
occurs no (automatic) transition to the message or command phase after selection, as in the usual cases after the
Wait_selection command.
(1) If only a target ID is selected after the Wait_select_cmd command is issued, an IDERR interrupt occurs
and the command is terminated.
The inside is in the condition where connection is complete, though. So message_out/command_out and
other commands can be issued, as in the usual case the selection is made with an initiator/target ID
(except that message_out/command_out is not executed automatically).
(2) If an ID of 3 bits or more is selected, an IDERR interrupt occurs. This distinguishes whether selection of
1 bit is completed or IDERR with an ID of 3 bits or more is selected.
If 1 bit is selected, IDERR and SEL interrupts occur. If ATN is not asserted here, a WOATN interrupt
occurs at the same time.
* The firm is asked to check that the SCSI-1 selection has occurred by observing the SEL interrupt at the
same time when an IDERR interrupt occurs.
Also, issue message_out/command_out manually while observing the state of WOATN interrupt, because
IDERR terminates the Wait_selection command.
