Hitachi Ultrastar 15K450 (FC-AL) Hard Disk Drive Specification
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21.0 Additional information
This chapter provides additional information or descriptions of various functions, features, or operating models supported by
the Target that are not fully described in previous chapters.

21.1 Obtaining an AL_PA

The SCA-2 FC-AL connector used by the drive provides 7 bits which encode a preferred Hard AL_PA for use on both loops.
If this value is set to 7Fh, a Soft AL_PA will be used.
Note: Loop Initialization cannot be bypassed if Soft AL_PA is selected.
A Soft AL_PA will also be used if, for any reason, the Hard AL_PA cannot be obtained. If this happens, The drive will
• log out all initiators
• accept new port logins
• accept each process login with a reason code of: 05h
No special action is taken if the connector supplied AL_PA is changed while the drive is participating on the loop(s).

21.2 Loop Initialization Procedure

L_Ports use the Loop Initialization Procedure in order to acquire an AL_PA and participate on the loop.
The drive optionally initiates the Loop Initialization Procedure shortly after power-on, depending on the configured mode set-
tings. In addition, it may (depending on the mode settings) initiate the Loop Initialization Procedure for the following reasons:
3. When it has been unable to obtain the loop for E_D_TOV.
4. When a loop failure has been detected (loss of sync for R_T_TOV)
The Loop Initialization Procedure is disruptive to any communication that is actually in progress on the loop. IOPs that are
queued or active but without any frames 'in flight' are not affected.
Initiators are not logged out by the Loop Initialization Procedure, but it is their responsibility to login if their AL_PA changes.
The drive detects (via the Port_Name) this situation and implicitly ends the prior login. The initiator may perform a 'Port Dis-
covery' sequence to check that the targets have not physically changed.
The L_Port that initiates the Loop Initialization Procedure must transmit LIPs for 2 x AL_TIME to ensure that all L_Ports par-
ticipate. By default, AL_TIME is set to 15ms.
All L_Ports must provide sufficient buffering to receive and transmit the LIxx frames that are circulated during the Loop Ini-
tialization Procedure. The largest of these (LILP and LIRP) have a 132 byte payload and are supported by the drive.