Identify Message: X'80' To X'ff' (I↔T) - Fujitsu MBA3073 SERIES Technical Manual

INIT renews the current data pointer according to the invalid number of data bytes notified by this
message.
Note:
The number of effective bytes of data which transfers by the data phase and boundary need
not use this message at the data out phase because TARG controls.
2.3.19 IDENTIFY message: X'80' to X'FF' (I↔T)
Bit 7
1
This message specifies the logical unit number (LUN) for the device (logical unit) under the
TARG and establishes an I/O operation path between the INIT, TARG, and logical unit.
a. Bit 6: Disconnect Privilege (D)
Only the INIT can set this bit to 1. When this bit is 1, it indicates that the INIT permits the
TARG to execute disconnection processing. When this bit is 0, the TARG must not execute
disconnection operation. When the TARG sends this message, this bit must be 0.
b. Bits 5 to 0: LUN
These bits specify the logical unit number (LUN) for the device.
Note:
The LUN of the HDD is fixed to #0.
c. Function of message
After the SELECTION phase has completed, the INIT usually sends the IDENTIFY message
to the TARG as the first message; this message specifies a logical unit for I/O operations.
Also, after the RESELECTION phase has completed, the TARG shall send the IDENTIFY
message to the INIT as the first message to inform the logical unit to be reconnected.
When an I/O operation path is established between the INIT and the TARG within a single
SELECTION or RESELECTION sequence, only a single LUN can be specified. The second
IDENTIFY message specifying a new LUN must not be issued until the SCSI bus is released
(that is, until a BUS FREE phase is generated). The INIT can send the IDENTIFY message
two or more times during a single I/O operation. In such case, value of bit 6 (Disconnect
Privilege) can be changed in the second and subsequent IDENTIFY messages. However, the
same LUN as specified by the first IDENTIFY message shall be specified in bits 5 to 0 (LUN).
C141-C015
6 5 4
D
3 2 1
LUN
0
167