Sun Oracle Storage Tek T10000, Reference Manual

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Error Detection and Management
42 T10000: Interface Reference Manual • January 2011 • E20425-01
Disparity
Fibre Channel uses a scheme along with the 8B/10B encoding to protect
transmission characters and aid in error detection called running disparity.
Running disparity adds a second dimension to the transmission of characters.
This dimension provides a balance of ones and zeros which helps protect
transmission characters and controls the heat output of the transmitter.
A negative running disparity is maintained following the transmission of the
end-of-frame (EOF) delimiter and remains negative until the transmission of
the next start-of-frame delimiter.
Because the running disparity within a frame is variable, two different EOF
delimiters are used depending on the content of the frame following the
transmission of the CRC.
CRC
Fibre Channel adds a third level of protection over the content of each frame
called a cyclic redundancy check (CRC). Each frame is protected by a 4-byte
CRC which provides a separate and independent error detection mechanism.
Table 23. 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