Sun Oracle Storage Tek T10000, Reference Manual

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Loop Initialization Features
18 T10000: Interface Reference Manual • January 2011 • E20425-01
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Loop Initialization Features
Arbitrated loop initialization protocol assigns up to a possible 126 addresses to
different ports on the loop and builds a map of these addresses. The following
pages describe some loop initialization features StorageTek tape drives
perform.
Loop initialization must occur before operations on the loop can begin. The
Loop Initialization Primitive (LIP) sequence is a series of initialization frames
that establish NL_Ports on the loop.
Any NL_Port on the loop is capable of starting an initialization sequence by
transmitting LIP. When the next NL_Port detects the LIP sequence, it
retransmits it to the next NL_Port until the LIP sequence travels around the
loop to the NL_Port initiating the sequence. During loop initialization, NL_Port
addresses (AL_PA) are assigned (x’01’ to x’EF’).
NL_Port addresses (AL_PA) can be either hard (hardware assigned) or soft
(system assigned) during loop initialization.
NL_Ports attempt to establish their previous acquired address before
attempting to acquire another address when that NL_Port is powered-on or
experiences a power-on reset, recognizes a LIP (AL_PD or AL_PS) for that
port, or any other event that causes the NL_Port to lose communications.
Note: StorageTek tape drives may use a hard assigned address and attempt
to regain that address during loop initialization. If unable to obtain that
address, the tape drives accept soft addresses by the system.
Acquiring Addresses
When an NL_Port enters the loop (such as a power-on), it begins initialization
to acquire an address and to notify other ports there is a change in
configuration.
Note: If there is an exchange in process when a LIP begins, that exchange is
disrupted and possible frame corruption could occur and result in a
ULP timeout.
• If the NL_Port does not have a valid address, it begins the initialization
sequence with LIP(F7,F7).
• If the NL_Port has a valid address, it begins initialization with LIP
(F7,AL_PS).