Hitachi HUS154530VLF400 User Manual

Hitachi Ultrastar 15K450 (FC-AL) Hard Disk Drive Specification

311 

The Port retransmits received ARB(F0) and prepares to receive the following frames, followed by CLS. 

a.   When a LIFA frame is received, the Port will set the bit corresponding to the Port’s “Fabric Assigned” AL_PA if the 

Port was logged-in to the local FL_Port prior to the LIP. (See 21.5, “Public Loop Operation” on page 312.) After 
transmitting the LIFA frame, The Port waits to receive a LIPA frame. 

b.   When a LIPA frame is received (and a bit was not set for LIPA), the bit corresponding to any previously assigned 

AL_PA is checked. If not set, it is set now. If it is already set, the Port attempts to obtain its Hard AL_PA in step c. 
The Port transmits the LIPA. 

c.   When a LIHA frame is received (and a bit was not set for LIPA), the bit corresponding to any required hard assigned 

AL_PA is checked. If not set, it is set now. If it is already set, the Port attempts to obtain a Soft AL_PA in step d. The 
Port transmits the LIHA. 

d.   When a LISA frame is received (and a bit was not set for LIHA), the bit associated with the lowest priority AL_PA 

still available is set. This is the Port’s soft assigned AL_PA. If no bits are available, the Port shall stay in non-partici-
pating mode. The Port transmits the LISA.

e.   If a LIRP frame is received, and the Port was able to claim an AL_PA in one of the LIxA frames, the left most byte 

is incremented by one and used as an offset at which to store the Port’s AL_PA. The Port transmits the LIRP. 

f.   If a LILP frame is received, the Port may store the AL_PA position map for use in error recovery. The Port transmits 

the LILP. 

g.   When CLS is received, the Port retransmits it and goes to MONITORING state. 

The drive provides a Class 3 service. Flow control is maintained using R_RDYs. 

Each initiator is required to login with every target. This establishes the Login BB_Credit, (i.e. how many frames the initiator 
or target may send immediately on opening or being opened.) 

Prior to login, BB_Credit is zero. 

The Alternate BB_Credit Model is operated as follows... 

•

On opening, the Available BB_Credit in each direction is set to the agreed Login BB_Credit value. 

•

Each frame sent decrements the Available BB_Credit and each R_RDY received increments it. 

•

If the Available BB_Credit reaches zero, the node must stop sending frames until enough R_RDYs have been 

received to restore positive credit. 

•

It is permissible to close before credit is balanced (i.e. R_RDY received for each frame sent) but only when enough 

buffers are available to satisfy the maximum Login BB_Credit that has been extended. 

Available BB_Credit may exceed Login BB_Credit but a point to note is that R_RDY is not specific to any frame type. There-
fore, the amount of Available BB_Credit that the drive will extend is limited by the amount of buffer space available for 
FCP_CMND or FCP_DATA IUs. For example, during the execution of a 512K WRITE command, there may be buffer space 
for 256 2K FCP_DATA IUs and 10 FCP_CMND IUs. The amount of credit extended will be for 10 frames. 

In order to communicate effectively, a pair of L_Ports must exchange operational parameters. The same applies to any SCSI 
processes that use the L_Ports. 

The exchange of parameters is called Login and may be either explicit or implicit. 

•

Explicit Login is the default. L_Ports use the PLOGI Extended Link Service sequence to exchange parameters and 

SCSI Processes use the PRLI Extended Link Service. 

•

Implicit Login is enabled via setting of mode page 19h. When enabled, PLOGI and PRLI are not required and a 

default set of parameters is assumed.