Fujitsu MCJ3230SS manual Message functions, SCSI Messages

4.4 SCSI Messages

4.4.3 Message functions

This section explains the function of each message. The symbols in the following explanations have the following meanings:

(I → T): Message that can only be sent from INIT to TARG

(T → I): Message that can only be sent from TARG to INIT

(I ←→ T): Message that can be sent between TARG and INIT in either direction

(1) COMMAND COMPLETE message: 00h (T → I)

The execution of a single command ended and valid status information was reported to INIT. The function of the message is to report the validity of status information; the message does not always indicate that the command ended normally. The command end status is indicated in the status byte transferred in the STATUS phase before the message is sent. Even if command transfer was not executed normally (because of such reasons as the occurrence of a parity error in the SCSI data bus in the MESSAGE OUT or COMMAND phase), TARG always sends this message after the STATUS phase if TARG reports the status byte to INIT.

After sending this message normally, TARG shifts to the BUS FREE phase. TARG assumes that message transmission was completed normally if the ATN signal is FALSE when the ACK signal changes to FALSE at the completion of the transfer of this message.

(2) SAVE DATA POINTER message: 02h (T → I)

This message instructs INIT to save the current data pointer.

(3) DISCONNECT message: 04h (T → I)

This message notifies INIT that TARG has temporarily disconnected the SCSI bus. After sending this message normally, TARG shifts to the BUS FREE phase to complete disconnection. TARG then continues command processing internally. It reconnects INIT when TARG needs to continue command execution on the SCSI bus.

(4) INITIATOR DETECTED ERROR message: 05h (I → T)

This message notifies TARG that INIT detected an error for which TARG can retry command processing. The cause of the error can be something related to operation on the SCSI bus or something attributable to INIT internal operation that is not directly related to operation on the SCSI bus.

(5) ABORT message: 06 (I - > T)

This message instructs TARG to clear the I/O operation being executed by INIT. Upon receipt of this message, TARG interrupts the current operation and shifts to the BUS FREE phase. The pending data and status related to the interrupted operation and sense data hold state are all cleared. This message has no effect on the operation started by another INIT.

C156-E224-01EN 4-43