FC-AL Features
46 SL500: Interface Reference Manual • July 2008 Revision: F • 96122
Because the running disparity within a frame is variable, two different EOF
delimiters are used (see TABLE 5-3), depending on the content of the frame
following the transmission of the CRC (see “CRC” on page 64).
FC-AL Features
Initialization and other processes take on special attributes and functions in an
arbitrated loop topology. The following sections explain these attributes and
functions as specified in the Fibre Channel Arbitrated Loop (FC-AL) specification.
Initialization
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
sections describe some loop initialization features that StorageTek libraries
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 (00h to EFh).
NL_Port addresses (AL_PA) can be either hard (hardware assigned) or soft (system
assigned) during loop initialization.
TABLE 5-3 End of Frame Delimiters
Delimiter Abbreviation RD Transmission Word Characters
EOF Normal EOFn Neg. K28.5 D21.4 D21.6 D21.6
Pos. K28.5 D21.5 D21.6 D21.6
EOF Terminate EOFt Neg. K28.5 D21.4 D21.3 D12.3
Pos. K28.5 D21.5 D21.3 D21.3
EOF Abort EOFa Neg. K28.5 D21.4 D21.7 D21.7
Pos. K28.5 D21.5 D21.7 D21.7
EOF Normal Invalid EOFni Neg. K28.5 D10.4 D21.6 D21.6
Pos. K28.5 D10.5 D21.6 D21.6
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