A.6 Messages

(7)BUS DEVICE RESET (X’0C’) : MESSAGE OUT phase (initiator → target)

This message addresses any initiators that are operating, or waiting for operation, on the target. The message initializes those initiators by resetting their input/ output operations.

The BUS DEVICE RESET message is transferred in the asynchronous mode. This scanner generates the UNIT ATTENTION condition to all initiators. After being initialized, the initiators move to the BUS FREE phase.

The initiators do not intend to issue another message by activating ATN before they deactivate the ACK of the BUS DEVICE RESET message.

(8)IDENTIFY (X’80’ to X’FF’) : MESSAGE OUT phase (initiator → target)

This message specifies either a logical unit under control of the target, or a process incorporated in the target (maintenance, self-diagnostic, etc.).

7

6

5

4

3

2

1

0

1

Specifies a logical unit number (for bit 4 = 0)

Specifies a process incorporated in the target (for bit = 1)

(Reserved)

(Reserved)

1:Processed by the target alone

0:Processed by the target and logical unit

1:The initiator does not permit disconnect

0:The initiator permits disconnect

Bit for distinguishing from other messages

This scanner does not support the target-incorporated process function. Therefore, if a 1 is set in bit 5, the IDENTIFY message is rejected with the MESSAGE REJECT message.

(9)DISCONNECT (X’04’): MESSAGE IN phase (target → initiator)

Sent from the target to the initiator, this message indicates that the current link will be disconnected but it will later have to be reconnected to complete the current process.

After successfully sending the DISCONNECT message, the target releases the BSY signal to switch into the BUS FREE phase. The target assumes the message transfer to be successful if it detects that the ATN signal as well as the ACK signal from the DISCONNECT message are false.

This scanner issues the DISCONNECT message if bit 6 (DiscPriv) in the IDENTIFY message from the initiator is 1 and if a long time is expected for processing in the scanner (e.g., when the scanner receives the READ command and prepares data to be transferred to the initiator).

Appendix A-111